tsar: restore gp register in crtn.S
tsar: restore gp register in crtn.S

This code was mostly taken from MIPS, but it seems weird that we
wouldn't need to restore gp register.

joel-porquet/tsar-uclibc,joel-porquet/tsar-uclibc,joel-porquet/tsar-uclibc,joel-porquet/tsar-uclibc