imx: hab: Provide hab_auth_img_or_fail command

This patch adds hab_auth_img_or_fail() a command line function that
encapsulates a common usage of authenticate and failover, namely if
authenticate image fails, then drop to BootROM USB recovery mode.

For secure-boot systems, this type of locked down behavior is important to
ensure no unsigned images can be run.

It's possible to script this logic but, when done over and over again the
environment starts get very complex and repetitive, reducing that script
repetition down to a command line function makes sense.

Signed-off-by: Bryan O'Donoghue <bryan.odonoghue@linaro.org>
Cc: Utkarsh Gupta <utkarsh.gupta@nxp.com>
Cc: Breno Lima <breno.lima@nxp.com>
Cc: Fabio Estevam <fabio.estevam@nxp.com>
Signed-off-by: Bryan O'Donoghue <bryan.odonoghue@linaro.org>
Tested-by: Breno Lima <breno.lima@nxp.com>