dt-bindings: pinctrl: Modify pinctrl memory map

Earlier, the PWM registers were included as part of the pinctrl memory
map, but this turned to be useless as the muxing is being handled by the
SoC pin controller itself. So, lets modify the pinctrl memory map to
reflect the same.

Fixes: 07b734fb ("dt-bindings: pinctrl: Add BM1880 pinctrl binding")
Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>