wil6210: improve debugfs for VRING

When printing VRING on debugfs (file "vrings"),
software head & tail indexes were printed in decimal format
while hardware tail in hexadecimal only.

It is not comfortable to compare indexes in different formats;
on the other hand, hexadecimal output useful to see hardware
glitches.

To serve all purposes, print hardware tail in both decimal and
hexadecimal formats.

Signed-off-by: Vladimir Kondratiev <qca_vkondrat@qca.qualcomm.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>