MIPS/LD: Skip overflow check for %pcrel_hi relocations

MIPS/LD: Skip overflow check for %pcrel_hi relocations

Overflow checks were removed for all hi16 relocations except PC-relative
high relocations per PR ld/16720.  Remove overflow checks from %pcrel_hi
relocations so that we can correctly handle negative offsets from PC.

bfd/
	* elfxx-mips.c (mips_elf_calculate_relocation) <R_MIPS_PCHI16>:
	Remove overflow check.

ld/
	* testsuite/ld-mips-elf/undefweak-overflow.s: Remove test case
	for pcrel_hi/pcrel_lo.
	* testsuite/ld-mips-elf/undefweak-overflow.d: Update to match.
	* testsuite/ld-mips-elf/reloc-pcrel-r6.s: New test source.
	* testsuite/ld-mips-elf/reloc-pcrel-r6.d: New test linker script.
	* testsuite/ld-mips-elf/reloc-pcrel-r6.ld: New test.
	* testsuite/ld-mips-elf/mips-elf.exp: Run the new test.