defconfig: ti: Add configs for OMAP5-class secure parts

Adds new defconfig files for DRA7xx and AM57xx secure devices.
These are the same as the non-secure parts, but with the addition
of the CONFIG_TI_SECURE_DEVICE option set to 'y'.

Signed-off-by: Daniel Allred <d-allred@ti.com>
Signed-off-by: Madan Srinivas <madans@ti.com>

Reviewed-by: Tom Rini <trini@konsulko.com>