GCC: fix type passed to vcvt_f32_f16 to be a float16x4_t in SkVx.h

GCC intrisics type validation is stricter than the one in Clang, so
passing a uint16x4_t to a function expected to accept float16x4_t
is not valid.

Bug: chromium:819294
Change-Id: I6d68e5458345e78bdb05dd028481fe9cae36c5ff
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/307276
Reviewed-by: Mike Klein <mtklein@google.com>
Commit-Queue: Mike Klein <mtklein@google.com>
1 file changed