[mips][microMIPS] Extending size reduction pass with ADDIUSP and ADDIUR1SP

Author: milena.vujosevic.janicic
The patch extends size reduction pass for MicroMIPS.
The following instructions are examined and transformed, if possible:
ADDIU instruction is transformed into 16-bit instruction ADDIUSP
ADDIU instruction is transformed into 16-bit instruction ADDIUR1SP
Usage of u_int64_t replaced by uint64_t to avoid issues because of which previous patch version was reverted:
Differential Revision: https://reviews.llvm.org/D34511

llvm-svn: 310044