staging: vt6655: fix camelcase in ldBmThreshold

staging: vt6655: fix camelcase in ldBmThreshold

Replace camel case variable ldBmThreshold with snake case
variable dbm_threshold. ldBmThreshold is in hungarian notation, where
"l" is for long and "dbm" is for decibel-milliwatt (signal strenght).
This variable contain's signal strenght threshold in dbm.

References:
 - https://en.wikipedia.org/wiki/Hungarian_notation
 - https://www.rapidtables.com/electric/dBm.html

Signed-off-by: Tommaso Merciai <tomm.merciai@gmail.com>
Link: https://lore.kernel.org/r/20211005205702.14029-3-tomm.merciai@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>