Input: iqs5xx - eliminate unnecessary register read

Input: iqs5xx - eliminate unnecessary register read

Instead of relying on firmware to enable important register fields
and performing read-modify-write operations to additionally enable
the fields the driver cares about, it's much simpler just to write
all of the pertinent fields explicitly.

This avoids an unnecessary register read operation at start-up and
makes way for the iqs5xx_read_byte() helper to be dropped.

Signed-off-by: Jeff LaBundy <jeff@labundy.com>
Link: https://lore.kernel.org/r/1611002626-5889-8-git-send-email-jeff@labundy.com
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>