[llvm] [MC] Fix clang integrated assembler generates incorrect relocations… (PR #83115)

[via llvm-commits]

yingopq wrote:

> I don't have more time spent on investigating the issue, but adding a lot of mips-specific code to the generic AsmParser.cpp is not acceptable.

@MaskRay Now we have two modification plans. 
The first one is in the ```files changed``` in this PR, which changes the starting point of the scan to ensure that the .rdata section is in front of the .text section; the second one is scan twice as recommended by @wzssyqa.

https://github.com/llvm/llvm-project/pull/83115