PR ld/20995: MIPS: Set GAS flags correctly for tests

Complement commit 9acc85a62eb7 ("Use dynrelro for symbols in relro
sections too").

	ld/
	PR ld/20995
	* testsuite/ld-elf/elf.exp: Set GAS flags correctly for the
	`mips*-*-*' target and `pr20995' and `pr20995-2' tests.
2 files changed