[mips] Extend LONG_BRANCH_LUi/ADDiu with extra parameter

Extend LONG_BRANCH_LUi and LONG_BRANCH_ADDiu pseudo instructions with
additional flag, so instead of always lowering to lui %hi(...),
addiu %lo(...) or addiu %hi(...), now they can lower to either %lo, %hi,
%higher or %highest depending on the added flag.

Differential Revision: https://reviews.llvm.org/D47941

llvm-svn: 334490