arm: imx: hab: Fix authenticate_image result code

arm: imx: hab: Fix authenticate_image result code

authenticate_image returns 1 for success and 0 for failure. That result
code is mapped directly to the result code for the command line function
hab_auth_img - which means when hab_auth_img succeeds it is returning
CMD_RET_FAILURE (1) instead of CMD_RET_SUCCESS (0).

This patch fixes this behaviour by making authenticate_image() return 0 for
success and 1 for failure. Both users of authenticate_image() as a result
have some minimal churn. The upshot is once done when hab_auth_img is
called from the command line we set $? in the standard way for scripting
functions to act on.

Fixes: 36c1ca4d46ef ("imx: Support i.MX6 High Assurance Boot
authentication")

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>