[ARM] 3137/1: RX3715 - fix map_desc initialiser

Patch from Ben Dooks

Change the initialiser for the map_desc for the
iPAQ RX3715 to use the new pfn initialiser, and
also reduce the amount of ISA space mapped (we
only need to stop any ISA IO writes OOPsing
the system, so do not need >1Mbyte of space)

Signed-off-by: Ben Dooks <ben-linux@fluff.org>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>