drivers: char: reset signal support for smd channels

Some user space client may be intersted in reset signals
when channel open or close happen due to ssr of remote
subsystem.

Adding support for reset signal for channel state changes.

Change-Id: Ice99c66b33f87ff94c870b4ee46cbd0d4f5023ee
Signed-off-by: Deepak Kumar Singh <deesin@codeaurora.org>