serial: icom: remove to_icom_adapter() and icom_kref_release()

Integrate both the to_icom_adapter() macro and icom_kref_release()
wrapper into icom_remove_adapter(). (And keep it icom_kref_release()
name.)

It makes the code easier to follow without complex indirections.

Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Link: https://lore.kernel.org/r/20220421085808.24152-4-jslaby@suse.cz


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>