Fixup convert-dfp*.c

The testcases use -save-temps which doesn't play nice with -flto
and multilib testing resulting in spurious UNRESOLVED like

/usr/lib64/gcc/x86_64-suse-linux/14/../../../../x86_64-suse-linux/bin/ld: i386:x86-64 architecture of input file `./convert-dfp-2.ltrans0.ltrans.o' is incompatible with i386 output

The following skips the testcases when using -flto.

	* gcc.dg/torture/convert-dfp-2.c: Skip with -flto.
	* gcc.dg/torture/convert-dfp.c: Likewise.