[Mips] Remove unused class field.
[Mips] Remove redundant call to the unique_ptr::get() method followed
by the returned pointer dereferencing.
[Mips] Remove redundant 'mips' prefix from names of MipsTargetHandler
and MipsDynamicSymbolTable classes fields.
[Mips] Mark class by 'final' keyword.
[Mips] Do not inherit MipsDynamicLibraryWriter and MipsExecutableWriter
from MipsELFWriter class. MipsELFWriter is just a helper.
[Mips] Remove unnecessary LLVM_ATTRIBUTE_UNUSED attribute.
[Mips] Change unused return type from 'bool' to 'void'.
[Mips] Reduce the code indentation.
[Mips] Remove redundant 'mips' prefix from names of MipsELFWriter class
fields.
[Mips] Rename R_MIPS_26 relocation handling test case.