[POWERPC] bootwrapper: missing relocation in crt0.S

crt0.S had provisions to provide run address relocaton to got2 and
cache flush, but not on the bss clear or stack pointer load.  Apply
the same fixup for them.

Signed-off-by: Milton Miller <miltonm@bga.com>
Signed-off-by: Paul Mackerras <paulus@samba.org>