sparc64: Add 64K page size support

This patch depends on:
[v6] sparc64: Multi-page size support

- Testing

Tested on Sonoma by running stream benchmark instance which allocated
48G worth of 64K pages.

boot params: default_hugepagesz=64K hugepagesz=64K hugepages=1310720

Signed-off-by: Nitin Gupta <nitin.m.gupta@oracle.com>
Signed-off-by: David S. Miller <davem@davemloft.net>