mtd: remove 'SBC8240 Wind River' Device Driver Code

This driver is causing build errors and is no longer needed -- it is obsoleted
by physmap_of.

Signed-off-by: Subrata Modak <subrata@linux.vnet.ibm.com>
Tested-on-PPC64-by: Subrata Modak <subrata@linux.vnet.ibm.com>
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>