staging: most: rename DIM_ServiceChannel to dim_service_channel

This patch renames DIM_ServiceChannel to dim_service_channel to avoid
camelcase found by checkpatch.

CHECK: Avoid CamelCase: <DIM_ServiceChannel>
FILE: drivers/staging/most/hdm-dim2/dim2_hal.c:857:

Signed-off-by: Chaehyun Lim <chaehyun.lim@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>