[XEN][POWERPC] Fix systemsim-gpul failure to boot

[XEN][POWERPC] Fix systemsim-gpul failure to boot
This patch fixes the fencepost error and adds a check for the failure to
initialize the allocator, which would have make Mark's FTB much easier
to debug.
This works for me on the public systemsim-gpul release.
Signed-off-by: Amos Waterland <apw@us.ibm.com>
Also fixes Maple, was just getting luck.
Signed-off-by: Jimi Xenidis <jimix@watson.ibm.com>
Signed-off-by: Hollis Blanchard <hollisb@us.ibm.com>
--HG--
extra : transplant_source : %87%8C%E1%F7%8A%D3%97oD%A6W%E58j%7Fma%9F%FA%C2