[POWERPC] Xilinx: hwicap: Refactor status handling code.

Both the buffer-based and fifo-based icap cores have a status
register.  Previously, this was only used internally to check whether
transactions have completed.  However, the status can be useful to the
main driver as well.  This patch exposes these status functions to the
main driver along with some masks for the differnet bits.

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>