ARM: ep93xx: add framebuffer to the defconfig

The EP93xx SoC has a framebuffer driver, let's add this to the
defconfig so we can have graphics working out of the box.

Reviewed-by: H Hartley Sweeten <hsweeten@visionengravers.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>