kernel: 5.4: backport fxos8700 accel support from 5.5

kernel: 5.4: backport fxos8700 accel support from 5.5

Backport kernel module from 5.5 for FXOS8700CQ, which is a small,
low-power, 3-axis linear accelerometer and 3-axis magnetometer combined
into a single package. The device features a selectable I2C or
point-to-point SPI serial interface with 14-bit accelerometer and 16-bit
magnetometer ADC resolution along with smart-embedded functions.

Signed-off-by: Tim Harvey <tharvey@gateworks.com>
[added commit description]
Signed-off-by: Petr Štetiar <ynezz@true.cz>