[ELF] Fix early overflow check in finalizeAddressDependentContent

LLD terminates with errors when it detects overflows in the
finalizeAddressDependentContent calculation. Although, sometimes, those errors
are not really errors, but an intermediate result of an ongoing address
calculation.  If we continue the fixed-point algorithm we can converge to the
correct result.

This patch

* Removes the verification inside the fixed point algorithm.
* Calls checkMemoryRegions at the end.

Reviewed By: peter.smith, MaskRay

Differential Revision: https://reviews.llvm.org/D152170