i386/asm-4 test: use amd64's natural addressing mode on all OSs

i386/asm-4 test: use amd64's natural addressing mode on all OSs

gcc.target/i386/asm-4.c uses amd64's natural PC-relative addressing
mode on a single platform, using the 32-bit absolute addressing mode
elsewhere.  There's no point in giving up amd64's natural addressing
mode and insisting on the 32-bit one when we're targeting amd64, and
having to make explicit exceptions for systems where that's found not
to work for whatever reason.  If we just use the best-suited way to
take the address of a function behind the compiler's back on each
target variant, we're less likely to hit unexpected failures.

for  gcc/testsuite/ChangeLog

	* gcc.target/i386/asm-4.c: Use amd64 natural addressing mode
	on all __LP64__ targets.

From-SVN: r274559