fix(plat/st): panic if boot interface is wrong

Add a panic() at the end of stm32mp_io_setup() if the boot interface
given in ROM code boot context is not supported.

Change-Id: I0d50f21a11231febd21041b6e63108cc3e6f4f0c
Signed-off-by: Yann Gautier <yann.gautier@foss.st.com>

plat/st/common/bl2_io_storage.c

@@ -651,6 +651,7 @@ void stm32mp_io_setup(void)
 	default:
 		ERROR("Boot interface %d not supported\n",
 		      boot_context->boot_interface_selected);
+		panic();
 		break;
 	}
 }