[SPARC64]: pass correct addr in get_fb_unmapped_area(MAP_FIXED)

Looks like the MAP_FIXED case is using the wrong address hint.  I'd
expect the comment "don't mess with it" means pass the request
straight on through, not change the address requested to -ENOMEM.

Signed-off-by: Chris Wright <chrisw@sous-sol.org>
Signed-off-by: David S. Miller <davem@davemloft.net>