MCAsmBackend,X86: Pass MCValue to fixupNeedsRelaxationAdvanced. NFC
This parameter eliminates a redundant computation for VK_ABS8 in X86 and
reduces reliance on shouldForceRelocation in relaxation decisions.
Note: `local: jmp local@plt` relaxes JMP. This behavior depends on
fixupNeedsRelaxation calling shouldForceRelocation, which might change
in the future.