sh: Fix store queue bitmap end.

The end of the store queue bitmap is miscalculated when searching
for a free range in sq_remap(), missing the PAGE_SHIFT shift that's
done in sq_api_init(). This runs in to workloads where we can scan
beyond the end of the bitmap.

Spotted by Paul Jackson:

	http://marc.theaimsgroup.com/?l=linux-kernel&m=116493191224097&w

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