[PATCH] PPC32 8xx: support for the physmapped flash on m8xx

Implemented more correct way to support physmapped flash on m8xx
than map in mtd.

The areas intended to contain bootloader are protected readonly.
Note that CFI and JEDEC stuff should be configured properly in order
this to work, e.g. for 885/86x CFI should support 4-chip flash interleave.
Also fixed compilation warning.

Signed-off-by: Vitaly Bordug <vbordug@ru.mvista.com>
Signed-off-by: Paul Mackerras <paulus@samba.org>