sh: Disable 64kB hugetlbpage size when using 64kB PAGE_SIZE.

Presently we oops in mm/hugetlb.c:1325, which is the order == 0 test in
hugetlb_add_hstate() called at initialization time. So, disable 64kB
huge pages when we're using a 64kB PAGE_SIZE. On most parts this will
force the default to be 1MB huge pages.

Signed-off-by: Paul Mundt <lethal@linux-sh.org>