Early in boot, reading MMRs from the UV hub controller require
calls to early_ioremap()/early_iounmap().  Rather than
duplicating code, add a common function to do the
map/read/unmap.
Signed-off-by: NJack Steiner <steiner@sgi.com>
LKML-Reference: <20101130195926.834804371@sgi.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>