i2c: bma250: gyro wake - keep sensor enabled when F2S is present

To let it work, when android framework would otherwise not
use the sensor (e.g. auto rotation is off)
i2c: bma250: gyro wake: adding f2w_sensitivity_values attr

to mark possible values and current sensitivity (for tweak apps)
e.g.: [0] 1 or 0 [1], showing 0 and 1 as possible values and which is
selected (with brackets).