configs: Add CONFIG_EXT4_ENCRYPTION=y

Enable EXT4 encryption support for all configurations except those
based on the original BCM2835, i.e. not on B+, Zero, etc. This
exception is because it would consume at least an additional 68KB,
which is a lot on a platform that may only have 128MB.

See: https://github.com/raspberrypi/linux/issues/2486



Signed-off-by: Phil Elwell <phil@raspberrypi.com>