[Mellanox] align platform_reboot to use "hardware reboot" (#3320)

Signed-off-by: Mykola Faryma <mykolaf@mellanox.com>

device/mellanox/x86_64-mlnx_msn2700-r0/platform_reboot

@@ -4,6 +4,7 @@ declare -r EXIT_SUCCESS="0"
 declare -r EXIT_ERROR="1"
 
 declare -r FW_UPGRADE_SCRIPT="/usr/bin/mlnx-fw-upgrade.sh"
+declare -r SYSFS_PWR_CYCLE="/sys/devices/platform/mlxplat/mlxreg-io/hwmon/hwmon*/pwr_cycle"
 
 FORCE_REBOOT="no"
 
@@ -20,7 +21,7 @@ function ParseArguments() {
 
 ParseArguments "$@"
 
-${FW_UPGRADE_SCRIPT} --upgrade
+${FW_UPGRADE_SCRIPT} --upgrade --verbose
 EXIT_CODE="$?"
 if [[ "${EXIT_CODE}" != "${EXIT_SUCCESS}" ]]; then
     echo "Failed to burn MLNX FW: errno=${EXIT_CODE}"
@@ -31,4 +32,6 @@ if [[ "${EXIT_CODE}" != "${EXIT_SUCCESS}" ]]; then
     fi
 fi
 
-exec /sbin/reboot $@
+echo 1 > $SYSFS_PWR_CYCLE
+sleep 3
+echo 0 > $SYSFS_PWR_CYCLE