arm: mach-k3: Remove ROM firewalls on GP devices

This isn't strictly needed as these firewalls should all be disabled on
GP, but it also doesn't hurt, so do this unconditionally to remove this
use of CONFIG_TI_SECURE_DEVICE.

Signed-off-by: Andrew Davis <afd@ti.com>
Reviewed-by: Tom Rini <trini@konsulko.com>