target-arm/neon_helper: Remove obsolete FIXME comment

Commit 33ebc293 fixed the bugs in the implementation of VQRSHL,
but forgot to remove the FIXME comment...
Signed-off-by: NPeter Maydell <peter.maydell@linaro.org>
Signed-off-by: NStefan Hajnoczi <stefanha@redhat.com>

target-arm/neon_helper.c

@@ -788,7 +788,6 @@ uint64_t HELPER(neon_qshlu_s64)(CPUARMState *env, uint64_t valop, uint64_t shift
     return helper_neon_qshl_u64(env, valop, shiftop);
 }
 
-/* FIXME: This is wrong.  */
 #define NEON_FN(dest, src1, src2) do { \
     int8_t tmp; \
     tmp = (int8_t)src2; \