loader/powerpc/ieee1275: Use new allocation function for kernel and initrd

loader/powerpc/ieee1275: Use new allocation function for kernel and initrd

On PowerVM and KVM on Power use the new memory allocation function that
honors restrictions on which memory GRUB can actually use. In the request
structure indicate the request for a single memory block along with
address alignment restrictions. Request direct usage of the memory block
by setting init_region to false (prevent it from being added to GRUB's
heap). Initialize the found addr to -1, so that -1 will be returned
to the loader in case no memory could be allocated.

Report an out-of-memory error in case the initrd could not be loaded.

Signed-off-by: Stefan Berger <stefanb@linux.ibm.com>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>
Cc: Hari Bathini <hbathini@linux.ibm.com>
Cc: Pavithra Prakash <pavrampu@in.ibm.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Carolyn Scherrer <cpscherr@us.ibm.com>
Cc: Mahesh Salgaonkar <mahesh@linux.ibm.com>
Cc: Sourabh Jain <sourabhjain@linux.ibm.com>