[POWERPC] Xilinx: hwicap: Use fixed device major.

Major 259 has been assigned by lanana.  Use it.  Also, publish
/dev/icap[0-k] as the device entries, and register platform devices
named 'icap' to be consistent.

Signed-off-by: Stephen Neuendorffer <stephen.neuendorffer@xilinx.com>
Acked-by: Grant Likely <grant.likely@secretlab.ca>
Signed-off-by: Josh Boyer <jwboyer@linux.vnet.ibm.com>