ARM: dts: ux500-skomer: Correct accel mounting matrix

This corrects the mounting matrix for the BMA254
accelerometer to what makes PostmarketOS actually
orient the screen the right way on this device.

Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Link: https://lore.kernel.org/r/20200719201603.3610389-1-linus.walleij@linaro.org