MIPS/LD/testsuite: Verify microMIPS LA25 stub generation

Repeat `PIC and non-PIC test 1' checks for microMIPS LA25 stubs,
covering code generation and stub symbol annotation.

	ld/
	* testsuite/ld-mips-elf/pic-and-nonpic-1-micromips-rel.dd: New
	test.
	* testsuite/ld-mips-elf/pic-and-nonpic-1-micromips-rel.nd: New
	test.
	* testsuite/ld-mips-elf/pic-and-nonpic-1-micromips.dd: New test.
	* testsuite/ld-mips-elf/pic-and-nonpic-1-micromips.nd: New test.
	* testsuite/ld-mips-elf/pic-and-nonpic-1a-micromips.s: New test
	source.
	* testsuite/ld-mips-elf/pic-and-nonpic-1b-micromips.s: New test
	source.
	* testsuite/ld-mips-elf/mips-elf.exp: Run the new tests.