toshiba_acpi: Add IIO interface for accelerometer axis data

This patch adds the accelerometer axis data to the IIO subsystem.

Currently reporting the X, Y and Z values, as no other data can be
queried given the fact that the accelerometer chip itself is hidden
behind the Toshiba proprietary interface.

Signed-off-by: Azael Avalos <coproscefalo@gmail.com>
Acked-by: Jonathan Cameron <jic23@kernel.org>
Signed-off-by: Darren Hart <dvhart@linux.intel.com>