Input: add driver for ADXL345/346 Digital Accelerometers

This is a driver for the ADXL345/346 Three-Axis Digital Accelerometers.

Signed-off-by: Michael Hennerich <michael.hennerich@analog.com>
Signed-off-by: Chris Verges <chrisv@cyberswitching.com>
Signed-off-by: Luotao Fu <l.fu@pengutronix.de>
Signed-off-by: Barry Song <barry.song@analog.com>
Signed-off-by: Mike Frysinger <vapier@gentoo.org>
Signed-off-by: Dmitry Torokhov <dtor@mail.ru>