ARM: at91/defconfig: add HLCDC driver to sama5_defconfig

Add the LCD DRM driver with all its dependencies:
- the MFD driver
- the backlight PWM
- the simple panel driver

Remove the CONFIG_FB as it is not needed on any sama5 device.

Signed-off-by: Nicolas Ferre <nicolas.ferre@atmel.com>
Acked-by: Alexandre Belloni <alexandre.belloni@free-electrons.com>