testsuite: Fix up amx* dg-do run tests with older binutils

testsuite: Fix up amx* dg-do run tests with older binutils

These tests were missing dg-requires-effective-targets to ensure they
are UNSUPPORTED if the assembler doesn't have AMX support.

2020-09-30  Jakub Jelinek  <jakub@redhat.com>

	* gcc.target/i386/amxint8-dpbssd-2.c: Require effective targets
	amx_tile and amx_int8.
	* gcc.target/i386/amxint8-dpbsud-2.c: Likewise.
	* gcc.target/i386/amxint8-dpbusd-2.c: Likewise.
	* gcc.target/i386/amxint8-dpbuud-2.c: Likewise.
	* gcc.target/i386/amxbf16-dpbf16ps-2.c: Require effective targets
	amx_tile and amx_bf16.
	* gcc.target/i386/amxtile-2.c: Require effective target amx_tile.