xpedite1k: Use standard CFI flash driver

Using the CFI flash driver will allow write access to the 16MB Intel
StrataFlash present on the XPedite1000.  The 512KB socketed (non
CFI-compliant flash) will no longer be writable.

The mapping of the 16MB Strata flash was moved to 0xff000000 and the
512KB AMD socketed flash was moved to 0xfe000000.

Signed-off-by: Peter Tyser <ptyser@xes-inc.com>
Signed-off-by: Stefan Roese <sr@denx.de>