arm: omap-common: add secure rom call API for secure devices

Adds a generic C-callable API for making secure ROM calls on OMAP and
OMAP-compatible devices. This API provides the important function of
flushing the ROM call arguments to memory from the cache, so that the
secure world will have a coherent view of those arguments. Then is
simply calls the omap_smc_sec routine.

Signed-off-by: Daniel Allred <d-allred@ti.com>
Signed-off-by: Andreas Dannenberg <dannenberg@ti.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Tom Rini <trini@konsulko.com>