Input: elants_i2c - fix for devm_gpiod_get API change

Flags are now mandatory for devm_gpiod_get(). So let's use proper flag
to configure gpio for output instead of doing this by hand.

Signed-off-by: Stephen Rothwell <sfr@canb.auug.org.au>
[Dmitry: GPIOD_ASIS -> GPIOD_OUT_LOW]
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>