Fix ixaddrs as well, allowing ppc64 to compile to:

_test2:
        li r2, 0
        lis r3, 1
        std r2, 9024(r3)
        blr

instead of:

_test2:
        lis r2, 1
        li r3, 0
        ori r2, r2, 9024
        std r3, 0(r2)
        blr

This implements CodeGen/PowerPC/LargeAbsoluteAddr.ll:test2

llvm-svn: 34373