mtd: maps/sa1100: fix section mismatch

Commit f0b1e589 changed sa1100_mtd_probe from __init to __devinit,
but missed to correct sa1100_setup_mtd definition accordingly, which
causes following warning:

WARNING: vmlinux.o(.devinit.text+0xf4): Section mismatch in reference from
 the function sa1100_mtd_probe() to the function .init.text:sa1100_setup_mtd()
The function __devinit sa1100_mtd_probe() references
a function __init sa1100_setup_mtd().
If sa1100_setup_mtd is only used by sa1100_mtd_probe then
annotate sa1100_setup_mtd with a matching annotation.

Signed-off-by: Dmitry Artamonow <mad_soft@inbox.ru>
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>