wil6210: [DEBUG] Improve Vring printing

Print '_' for the 'idle' descriptors - this makes vring representation more visible.
Also, for the Tx side, differentiate descriptors having associated skb's - print ones
with skb as 'H' and without as 'h'. Good to represent scattered frames.

Signed-off-by: Vladimir Kondratiev <qca_vkondrat@qca.qualcomm.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
Git-commit: 59f7c0a9577a965e279a0c15858480100f28f03d
Git-repo: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git


Signed-off-by: Liron Kuch <lkuch@codeaurora.org>