staging: hv: Remove camel case variables in channel.c

Rename camel case variables in channel.c and changed them to
lowercase.

Signed-off-by: Haiyang Zhang <haiyangz@microsoft.com>
Signed-off-by: Hank Janssen <hjanssen@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>