ARM: defconfig: integrator: Switch to DRM

This switches the ARM Integrator to use the new PL11x DRM
driver. We need CMA enabled to get coherent allocations
at all times. The dumb VGA DAC bridge is needed for
the VGA output on the reference designs, and backlight
is needed when using an external display.

Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>