get_unmapped_area handles MAP_FIXED on alpha

Handle MAP_FIXED in alpha's arch_get_unmapped_area(), simple case, just return
the address as passed in

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Richard Henderson <rth@twiddle.net>
Cc: Ivan Kokshaysky <ink@jurassic.park.msu.ru>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>