ARM: at91/tclib: take iomem size from resource

Requesting iomem region and ioremaping is now done using
the resource size specified instead of a constant value.

Each <SoC>_device.c file is modified accordingly to reflect
actual user interface size.

Signed-off-by: Nicolas Ferre <nicolas.ferre@atmel.com>
Acked-by: Jean-Christophe PLAGNIOL-VILLARD <plagnioj@jcrosoft.com>