MLK-22836 imx8m: soc: Fix secure boot support for i.MX8MM and i.MX8MN targets

MLK-22836 imx8m: soc: Fix secure boot support for i.MX8MM and i.MX8MN targets

Since commit c98b47f1ff60 ("MLK-22749 imx8mq: Add workaround to fix sticky
bits lock up") it's not possible to build i.MX8MM and i.MX8MN targets with
CONFIG_SECURE_BOOT enabled:

  CC      cmd/version.o
arch/arm/mach-imx/imx8m/soc.c:326:23: error: ‘CONFIG_IMX_UNIQUE_ID’ undeclared \
(first use in this function); did you mean ‘CONFIG_IMX_VIDEO_SKIP’?
   if (!is_uid_matched(CONFIG_IMX_UNIQUE_ID))
                       ^~~~~~~~~~~~~~~~~~~~

The OCOTP sticky bit workaround is only needed for i.MX8MQ devices, other devices
should not build the secure_lockup() function.

Add CONFIG_IMX8MQ to the conditional compilation to avoid such issue.

Fixes: c98b47f1ff60 ("MLK-22749 imx8mq: Add workaround to fix sticky bits lock up")
Signed-off-by: Breno Lima <breno.lima@nxp.com>
Reviewed-by: Ye Li <ye.li@nxp.com>
(cherry picked from commit be033bff3c718e8bd7d4ac5ecfe4361892fc6e61)