PR ld/15428: MIPS/LD/testsuite: Un-KFAIL `__ehdr_start' test 2

Complement commit b75d42bc ("Fix mips segfault on GOT access of
absolute symbol") and unmark the `__ehdr_start' test 2 as known to fail
for the n32 and n64 ABIs, as with the change referred in place the
causing issue has been properly addressed and consequently the tests do
not fail anymore and neither are supposed to.

	ld/
	PR ld/15428
	* testsuite/ld-mips-elf/mips-elf.exp: Un-KFAIL `__ehdr_start'
	test 2.