lavc/vp8dsp: disable EPEL HV on RV128

RV128 is mostly scifi at this point, so we can just disable it here
(the EPEL HV prologue/epilogue do not save 128-bit registers).

libavcodec/riscv/vp8dsp_init.c

@@ -97,7 +97,7 @@ av_cold void ff_vp78dsp_init_riscv(VP8DSPContext *c)
         c->put_vp8_epel_pixels_tab[0][1][0] = ff_put_vp8_epel16_v4_rvv;
         c->put_vp8_epel_pixels_tab[1][1][0] = ff_put_vp8_epel8_v4_rvv;
         c->put_vp8_epel_pixels_tab[2][1][0] = ff_put_vp8_epel4_v4_rvv;
-
+#if __riscv_xlen <= 64
         c->put_vp8_epel_pixels_tab[0][2][2] = ff_put_vp8_epel16_h6v6_rvv;
         c->put_vp8_epel_pixels_tab[1][2][2] = ff_put_vp8_epel8_h6v6_rvv;
         c->put_vp8_epel_pixels_tab[2][2][2] = ff_put_vp8_epel4_h6v6_rvv;
@@ -110,6 +110,7 @@ av_cold void ff_vp78dsp_init_riscv(VP8DSPContext *c)
         c->put_vp8_epel_pixels_tab[0][1][2] = ff_put_vp8_epel16_h6v4_rvv;
         c->put_vp8_epel_pixels_tab[1][1][2] = ff_put_vp8_epel8_h6v4_rvv;
         c->put_vp8_epel_pixels_tab[2][1][2] = ff_put_vp8_epel4_h6v4_rvv;
+#endif
     }
 #endif
 #endif

libavcodec/riscv/vp8dsp_rvv.S

@@ -321,8 +321,10 @@ epel \len 6 h
 epel \len 4 h
 epel \len 6 v
 epel \len 4 v
+#if __riscv_xlen <= 64
 epel_hv \len 6 6
 epel_hv \len 4 4
 epel_hv \len 6 4
 epel_hv \len 4 6
+#endif
 .endr