fixed typo in create_ip: set BLOCK_RAM B port to 256
fixed typo in create_ip: set BLOCK_RAM B port to 256

Signed-off-by: Thomas Fuchs <15897a30a83827a951186749e444341d3eb9178d@de.ibm.com>

open-power/snap,open-power/snap,open-power/snap,open-power/snap,open-power/snap