staging: most: fix argument name of DIM_GetChannelState

The second argument name of DIM_GetChannelState declaration changes from
dim_ch_state_ptr to state_ptr. The DIM_GetChannelState declaration and
definition has same argument name as state_ptr.

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