arm: imx: hab: Implement hab_rvt_check_target

This patch implements the basic callback hooks for hab_rvt_check_target()
for BootROM code using the older BootROM address layout - in my test case
the i.MX7. Code based on new BootROM callbacks will just have HAB_SUCCESS
as a result code. Adding support for the new BootROM callbacks is a TODO.

Signed-off-by: Bryan O'Donoghue <bryan.odonoghue@linaro.org>
Cc: Stefano Babic <sbabic@denx.de>
Cc: Fabio Estevam <fabio.estevam@nxp.com>
Cc: Peng Fan <peng.fan@nxp.com>
Cc: Albert Aribaud <albert.u.boot@aribaud.net>
Cc: Sven Ebenfeld <sven.ebenfeld@gmail.com>
Cc: George McCollister <george.mccollister@gmail.com>
Cc: Breno Matheus Lima <brenomatheus@gmail.com>
Tested-by: Breno Lima <breno.lima@nxp.com>
Reviewed-by: Fabio Estevam <fabio.estevam@nxp.com>