char: xilinx_hwicap: missing error code if ioremap() fails

Return -ENOMEM instead of success if ioremap() fails.

Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Reviewed-by: Jingoo Han <jg1.han@samsung.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>