char: xilinx_hwicap: Fix warnings in the driver

This patch fixes the below warning
        --> Use #include <linux/io.h> instead of <asm/io.h>
        --> Use #include <linux/uaccess.h> instead of <asm/uaccess.h>
        --> please, no space before tabs
        --> Block comments use a trailing */ on a separate line
        --> Possible unnecessary 'out of memory' message
        --> Block comments use * on subsequent lines
        --> Block comments use a trailing */ on a separate line
        --> braces {} are not necessary for any arm of this statement
        --> DT compatible string "xlnx,opb-hwicap-1.00.b"
	    appears un-documented
        --> DT compatible string "xlnx,xps-hwicap-1.00.a"
            appears un-documented

Signed-off-by: Nava kishore Manne <navam@xilinx.com>
Signed-off-by: Michal Simek <michal.simek@xilinx.com>
Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>