powerpc/virtex: fix various format/casting printk mismatches

Various printk format string in code used by the Xilinx Virtex platform
are not 32-bit/64-bit safe.  Add correct casting to fix the bugs.

Reported-by: Josh Boyer <jwboyer@linux.vnet.ibm.com>
Signed-off-by: Grant Likely <grant.likely@secretlab.ca>
Acked-by: Josh Boyer <jwboyer@linux.vnet.ibm.com>