LoongArch: ld: Add support for tls le relax.

LoongArch: ld: Add support for tls le relax.

Add tls le relax related testsuites in ld.

The new test cases are mainly tested in three aspects:

1. tls le relax function correctness test.
2. tls le relax boundary check test.
3. tls le relax function compatibility test.

ld/testsuite/ChangeLog:

	* ld/testsuite/ld-loongarch-elf/relax.exp: Modify test.
	* ld/testsuite/ld-loongarch-elf/old-tls-le.s: New test.
	* ld/testsuite/ld-loongarch-elf/relax-bound-check-tls-le.s: Likewise.
	* ld/testsuite/ld-loongarch-elf/tls-relax-compatible-check-new.s: Likewise.
	* ld/testsuite/ld-loongarch-elf/relax-tls-le.s: Likewise.
	* ld/testsuite/ld-loongarch-elf/tls-relax-compatible-check-old.s: Likewise.