[arm] Use -march=armv7-a+fp when testing hard-float

Some tests explicitly test with -march=armv7-a and -mfloat-abi=hard.
However, with the new -mfpu=auto code, this architectural specifiction
lacks any floating-point capabilities.  To rectify this, change the
architecture to armv7-a+fp.

gcc/testsuite:

	* gcc.dg/pr59418.c: On ARM, change architecture to armv7-a+fp.
	* gcc.target/arm/pr51915.c: Likewise.
	* gcc.target/arm/pr52006.c: Likewise.
	* gcc.target/arm/pr53187.c: Likewise.

From-SVN: r249299