char: xilinx_hwicap: Checkpatch.pl cleanup

Remove checkpatch warning:
WARNING: Use #include <linux/io.h> instead of <asm/io.h>

Signed-off-by: Michal Simek <michal.simek@xilinx.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>