input: sensors: fix the resolution of akm09911 configuration

The resolution of akm09911 is 0.6uT/LSB, so fix it in order to make
it compatible with sensor HAL.

Change-Id: I182511a9700f9ea9c0fbd9549a4bfa00d92d8fc4
Signed-off-by: Oliver Wang <mengmeng@codeaurora.org>