[ELF][MIPS] Support some of R_MIPS_PCxxx relocations
The patch adds support for R_MIPS_PC16, R_MIPS_PC19_S2, R_MIPS_PC21_S2, R_MIPS_PC26_S2, R_MIPS_PCHI16, R_MIPS_PCLO16 relocations handling.