wil6210: interrupt statistics

Track number of interrupts and Tx/Rx packets;
expose through debugfs 'info'. Reset upon read.
Used to analyse effectivness of interrupt coalescing and NAPI.
Read twice with some interval like
cat info > /dev/null; sleep 1; cat info

Change-Id: Iba34e3e6f4e4c4e4e4a67f23c56e8817e6ef9145
Signed-off-by: Vladimir Kondratiev <qca_vkondrat@qca.qualcomm.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
Git-commit: be299858d0611ee9f43fab7fa6dbea8671748267
Git-repo: git://git.kernel.org/pub/scm/linux/kernel/git/linville/wireless-testing.git


Signed-off-by: Hamad Kadmany <hkadmany@codeaurora.org>