HID: intel-ish-hid: Move the common functions from client.h

Move the interface functions in client.h to common include. These are
already abstracted well to use as is. Also move any associated structures
used by these functions.

Signed-off-by: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>