testsuite: arm: Tighten compile options for short-vfp-1.c [PR119556]

testsuite: arm: Tighten compile options for short-vfp-1.c [PR119556]

The previous version of this test required arch v6+ (for sxth), and
the number of vmov depended on the float-point ABI (where softfp
needed more of them to transfer floating-point values to and from
general registers).

With this patch we require arch v7-a, vfp FPU and -mfloat-abi=hard, we
also use -O2 to clean the generated code and convert
scan-assembler-times directives into check-function-bodies.

Tested on arm-none-linux-gnueabihf and several flavours of
arm-none-eabi.

gcc/testsuite/ChangeLog:

	PR target/119556
	* gcc.target/arm/short-vfp-1.c: Improve dg directives.