ARM: defconfig: Enable PL11x DRM driver on multi_v7

This switches the ARMv7 defconfig away from the old
fbdev driver to the new DRM driver. All machines are
now supported by the new driver.

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