From: Paul Mundt <lethal@linux-sh.org>

This implements hugetlb support for SH-4.  SH-4 supports 1k/4k/64k/1MB pages,
since we're only interested in the 64k/1MB sizes, this is what we support.

The sh hugetlbpage code borrows heavily off of the sparc64 port, which works
fine for these cases at this point in time.