cxlflash: shift wrapping bug in afu_link_reset()

"port_sel" is a u64 so the shifting should also be a 64 bit shift.

Fixes: c21e0bbf ('cxlflash: Base support for IBM CXL Flash Adapter')
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Reviewed-by: Johannes Thumshirn <jthumshirn@suse.de>
Acked-by: Matthew R. Ochs <mrochs@linux.vnet.ibm.com>
Signed-off-by: James Bottomley <JBottomley@Odin.com>