sm501: fix missing uses of resource_size()

There are several places in the SM501 fb driver that could do with using
resource_size() to calculate the size of a resource.

Also fix a bug where request_mem_region() is being passed one too few
bytes when requesting the register memory region, which was causing the
following in /proc/iomem:

 13e80000-13e8ffff : sm501-fb.0
   13e80000-13e8fffe : sm501-fb

fixed, this reads:

 13e80000-13e8ffff : sm501-fb.0
   13e80000-13e8ffff : sm501-fb

Signed-off-by: Ben Dooks <ben@simtec.co.uk>
Signed-off-by: Simtec Linux Team <linux@simtec.co.uk>
Cc: Vincent Sanders <vince@simtec.co.uk>
Cc: Krzysztof Helt <krzysztof.h1@poczta.fm>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>