m68knommu: make 520x QSPI platform addressing consistent

If we make all QSPI (SPI protocol) addressing consistent across all ColdFire
family members then we will be able to remove the duplicated plaform data
and code and use a single setup for all.

So modify the ColdFire 520x QSPI addressing so that:

. base addresses are absolute (not relative to MBAR peripheral register)
. use a common name for IRQs used
. move chip select definitions (CS) to appropriate header

Signed-off-by: Greg Ungerer <gerg@uclinux.org>