Revert "arm64/fpsimd: Fix merging of FPSIMD state during signal return"

This reverts commit 4bdbf1a6 which is
commit c94f2f32 upstream.

It breaks the Android kernel builds and can be brought back in the
future in an safe way if it is really needed.

Bug: 161946584
Change-Id: I61b23cafa960517528883d40ef581ee1963a8b13
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>