drm/pl111: Drop special pads config check

This drops the check of the surplus "pads" configuration
from the device tree that is completely unused in the DRM
driver.

This was only used to work around limitations in the earlier
fbdev driver.

Cc: Pawel Moll <pawel.moll@arm.com>
Cc: Liviu Dudau <Liviu.Dudau@arm.com>
Reviewed-by: Sam Ravnborg <sam@ravnborg.org>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20190724134959.2365-2-linus.walleij@linaro.org