staging: unisys: fix CamelCase name in virthba_probe()

Fix CamelCase local variable name:

pChannelHeader => channel_header

Update references to use the new name.

Signed-off-by: Benjamin Romer <benjamin.romer@unisys.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>