ARM: configs: at91_dt: resync with media changes

The media tree Kconfig has changed recently, and a lot of modules were
built unintentionally, like the dvb frontends and encoders.
Resync the defconfig to build the ISI drivers and tested sensors.

Signed-off-by: Eugen Hristev <eugen.hristev@microchip.com>
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Link: https://lore.kernel.org/r/20201029121223.871531-1-eugen.hristev@microchip.com