This patch add 'verext' debugfs item, which can be used to
get detailed chip specific information from our firmware.

Examples:
echo "1" > /sys/kernel/debug/mwifiex/mlan0/verext
cat /sys/kernel/debug/mwifiex/mlan0/verext
Signed-off-by: NShengzhen Li <szli@marvell.com>
Signed-off-by: NAmitkumar Karwar <akarwar@marvell.com>
Signed-off-by: NKalle Valo <kvalo@codeaurora.org>