arch:arm:mmp:gplugd: Fix gPlugD reboot issue

Board hangs in u-boot after issuing reboot related
commands from Linux console due to not resetting
Timer registers in the platform reset function which uses
generic softreset. Fixing the issue by adding board reset
code for gPlugD.

Signed-off-by: Ashokkumar G <0xfee1dead.sa@gmail.com>