stm32mp: stm32prog: add CONFIG_CMD_STM32PROG_OTP

Add a configuration flag CONFIG_CMD_STM32PROG_OTP to enable the support of
OTP update in stm32prog command.

This new configuration allows to deactivate this feature for security reason
and it is a preliminary step for support of OPT update with the OP-TEE
provisioning TA.

Signed-off-by: Patrick Delaunay <patrick.delaunay@foss.st.com>
Reviewed-by: Patrice Chotard <patrice.chotard@foss.st.com>
Signed-off-by: Patrice Chotard <patrice.chotard@foss.st.com>