Input: elants - refactor elants_i2c_execute_command()

Apply some DRY-ing to elants_i2c_execute_command() callers.  This pulls
polling and error printk()s into a single function.

Signed-off-by: Michał Mirosław <mirq-linux@rere.qmqm.pl>
Link: https://lore.kernel.org/r/6c576f688b385235c65b461410a917080d27e825.1587923061.git.mirq-linux@rere.qmqm.pl


Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>