[ARM] 3425/1: xsc3: need to include pgtable-hwdef.h

Patch from Lennert Buytenhek

Adapt xsc3 to the changes in 74945c86
(xsc3 was written before but merged after the latter went in.)

Signed-off-by: Lennert Buytenhek <buytenh@wantstofly.org>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>