HID: logitech-hidpp: Use 'atomic_inc_return' instead of hand-writing it

This function logs a warning if the workqueue gets too big.
In order to save a few cycles, use 'atomic_inc_return()' instead of an
'atomic_inc()/atomic_read()' sequence.

This axes a line of code and saves a 'atomic_read()' call.

Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>