serial: pch: inline pop_tx() into handle_tx()

Given pop_tx() is a simple loop, inline it directly into handle_tx().

The code in handle_tx() looks much saner and straightforward now.

Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Link: https://lore.kernel.org/r/20220503080808.28332-6-jslaby@suse.cz


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