board: ti: beagleboneai: add initial support

These are necessities for beaglebone ai boot. There is the addition of
CONFIG_SUPPORT_EMMC_CONFIG to the Kconfig file. This is present upstream
but not in 19.01 yet.

Signed-off-by: Jason Kridner <jdk@ti.com>
Signed-off-by: Caleb Robey <c-robey@ti.com>
Signed-off-by: Lokesh Vutla <lokeshvutla@ti.com>