ipg_stop from GPC is not connected to WDOG directly, the sec_debug clock is
used to sample the ipg_stop from GPC. So when this clock is off, ipg_stop input
of WDOG can’t assert, WDOG will fail to stop in DSM mode.
Enable this clock forever in SPL, so other SW don't need to touch it.

Signed-off-by: Ye Li <ye.li@nxp.com>
Tested-by: Bai Ping <ping.bai@nxp.com>
(cherry picked from commit 1da6c9b3a837d15c25086af449462d5e8b56c290)