Bluetooth: Removal of unused variable in btmrvl driver

This patch removes unused variable "drvdbg" from btmrvl_debugfs_data
structure.

Signed-off-by: Rahul Tank <rahult@marvell.com>
Signed-off-by: Bing Zhao <bzhao@marvell.com>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>