testsuite: Move pr123286.c to gcc.target/aarch64/

The test for PR middle-end/123286 unconditionally includes <arm_neon.h>
which is only available on AArch64 targets. Hence, move the testcase to
gcc.target/aarch64/ where the target context is implicit.

gcc/testsuite/ChangeLog:
	* gcc.dg/pr123286.c: Move to...
	* gcc.target/aarch64/pr123286.c: ...here.

Signed-off-by: Naveen <naveen.siddegowda@oss.qualcomm.com>

diff --git a/gcc/testsuite/gcc.dg/pr123286.c b/gcc/testsuite/gcc.target/aarch64/pr123286.c
similarity index 100%
rename from gcc/testsuite/gcc.dg/pr123286.c
rename to gcc/testsuite/gcc.target/aarch64/pr123286.c