Merge pull request #26071 from tingboliao:4.x

Remove the redundant codes of cv::convertMaps and mRGBA2RGBA<uchar> #26071

(1) cv::convertMaps: the branch [else if( m1type == CV_32FC2 && dstm1type == CV_16SC2 ) if( nninterpolate )] is unreachable,
    as the condition is satisfied in lines 1959 to 1961, calculated in advance and return directly.
(2) mRGBA2RGBA<uchar>: dst[0], dst[1], dst[2] and dst[3] is calculated repeatedly. Introduced in https://github.com/opencv/opencv/pull/13440

### Pull Request Readiness Checklist

See details at https://github.com/opencv/opencv/wiki/How_to_contribute#making-a-good-pull-request

- [ ] I agree to contribute to the project under Apache 2 License.
- [ ] To the best of my knowledge, the proposed patch is not based on a code under GPL or another license that is incompatible with OpenCV
- [ ] The PR is proposed to the proper branch
- [ ] There is a reference to the original bug report and related work
- [ ] There is accuracy test, performance test and test data in opencv_extra repository, if applicable
      Patch to opencv_extra has the same branch name.
- [ ] The feature is well documented and sample code can be built with the project CMake

modules/imgproc/src/color_rgb.simd.hpp

@@ -1088,11 +1088,6 @@ struct mRGBA2RGBA<uchar>
 
             uchar v3_half = v3 / 2;
 
-            dst[0] = (v3==0)? 0 : (v0 * max_val + v3_half) / v3;
-            dst[1] = (v3==0)? 0 : (v1 * max_val + v3_half) / v3;
-            dst[2] = (v3==0)? 0 : (v2 * max_val + v3_half) / v3;
-            dst[3] = v3;
-
             dst[0] = (v3==0)? 0 : saturate_cast<uchar>((v0 * max_val + v3_half) / v3);
             dst[1] = (v3==0)? 0 : saturate_cast<uchar>((v1 * max_val + v3_half) / v3);
             dst[2] = (v3==0)? 0 : saturate_cast<uchar>((v2 * max_val + v3_half) / v3);

modules/imgproc/src/imgwarp.cpp

@@ -2081,24 +2081,6 @@ void cv::convertMaps( InputArray _map1, InputArray _map2,
             }
         }
         else if( m1type == CV_32FC2 && dstm1type == CV_16SC2 )
-        {
-            if( nninterpolate )
-            {
-                #if CV_SIMD128
-                int span = VTraits<v_float32x4>::vlanes();
-                {
-                    for( ; x <= (size.width << 1) - span * 2; x += span * 2 )
-                        v_store(dst1 + x, v_pack(v_round(v_load(src1f + x)),
-                                                 v_round(v_load(src1f + x + span))));
-                }
-                #endif
-                for( ; x < size.width; x++ )
-                {
-                    dst1[x*2] = saturate_cast<short>(src1f[x*2]);
-                    dst1[x*2+1] = saturate_cast<short>(src1f[x*2+1]);
-                }
-            }
-            else
         {
             #if CV_TRY_SSE4_1
             if( useSSE4_1 )
@@ -2143,7 +2125,6 @@ void cv::convertMaps( InputArray _map1, InputArray _map2,
                 }
             }
         }
-        }
         else if( m1type == CV_16SC2 && dstm1type == CV_32FC1 )
         {
             #if CV_SIMD128