counter: Implement signalZ_action_component_id sysfs attribute

The Generic Counter chrdev interface expects users to supply component
IDs in order to select Synapses for requests. In order for users to know
what component ID belongs to which Synapse this information must be
exposed. The signalZ_action_component_id attribute provides a way for
users to discover what component ID belongs to the respective Synapse.

Cc: Gwendal Grignou <gwendal@chromium.org>
Cc: Dan Carpenter <dan.carpenter@oracle.com>
Reviewed-by: David Lechner <david@lechnology.com>
Signed-off-by: William Breathitt Gray <vilhelm.gray@gmail.com>
Link: https://lore.kernel.org/r/a6c81b2f1f5d0b8d59b1ebe4f0fed04914b07547.1632884256.git.vilhelm.gray@gmail.com
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>