testsuite: arm: Simplify fp16-aapcs tests

testsuite: arm: Simplify fp16-aapcs tests

Reduce fp16-aapcs testcases to return value testing since parameter
passing are already tested in aapcs/vfp*.c

gcc/testsuite/ChangeLog:
	* gcc.target/arm/fp16-aapcs.c: New test.
	* gcc.target/arm/fp16-aapcs-1.c: Removed.
	* gcc.target/arm/fp16-aapcs-2.c: Likewise.
	* gcc.target/arm/fp16-aapcs-3.c: Likewise.
	* gcc.target/arm/fp16-aapcs-4.c: Likewise.

Signed-off-by: Torbjörn SVENSSON <torbjorn.svensson@foss.st.com>