[TEMP] fix(scmi): Disable nonsecure memory mapped timer before powerdown

When idle states are enable, Linux kernel uses the memory mapped timer
to generate wake events periodicaly. Linux is not disabling the timer on
shutdown. Due to this, the timer continue to generate interrupts, and
which wakes the CPU core on warm reboot. To fix this, disable the memory
mapped timer before putting the secondary CPUs in dynamic OFF.

Change-Id: I9be32fe42919bdccf39af8b7675d2ef70e8dcde5
Signed-off-by: Pranav Madhu <pranav.madhu@arm.com>