arm64: Fix wrong BTI landing pad

This patch fixes a wrong type of BTI landing pad when branching to
functions instantiated via the fft*_neon macro.

Although the previously employed paciasp instruction serves as a landing
pad, for the ways that this function is invoked it is the wrong type, resulting
in an unexpected termination of the running process.

Signed-off-by: André Kempe <andre.kempe@arm.com>
Signed-off-by: Martin Storsjö <martin@martin.st>

libavcodec/aarch64/fft_neon.S

@@ -340,6 +340,7 @@ endfunc
 
 .macro  def_fft n, n2, n4
 function fft\n\()_neon, align=6
+        AARCH64_VALID_JUMP_TARGET
         AARCH64_SIGN_LINK_REGISTER
         sub             sp,  sp,  #16
         stp             x28, x30, [sp]