All K3 boards now are secure by default, instead of setting this in each
defconfig, make it implied by the ARCH config.
The only exception is IOT2050, which I do not believe will have any
problems with being a TI_SECURE_DEVICE, but for now turn it off to keep
its config the same.
Signed-off-by: Andrew Davis <afd@ti.com>
Tested-by: Tom Rini <trini@konsulko.com>