kern/ieee1275/init/ppc64: Rename regions_claim() to grub_regions_claim()

kern/ieee1275/init/ppc64: Rename regions_claim() to grub_regions_claim()

Rename regions_claim() to grub_regions_claim() to make it available for
memory allocation. The ieee1275 loader will use this function on PowerVM
and KVM on Power and thus avoid usage of memory that it is not allowed
to use.

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>