[PATCH] testsuite: constraint some of fp tests to hard_float

[PATCH] testsuite: constraint some of fp tests to hard_float

These tests validate fp conversions with various rounding modes which
would not work on soft-float ABIs.

On -march=rv64imac/-mabi=lp64 this reduces 5 unique failures (overall 35
due to multi flag combination builds)

gcc/testsuite/Changelog:
	* gcc.dg/torture/fp-double-convert-float-1.c: Add
	dg-require-effective-target hard_float.
	* gcc.dg/torture/fp-int-convert-timode-3.c: Ditto.
	* gcc.dg/torture/fp-int-convert-timode-4.c: Ditto.
	* gcc.dg/torture/fp-uint64-convert-double-1.c: Ditto.
	* gcc.dg/torture/fp-uint64-convert-double-2.c: Ditto.