cmd: boot: add mode args for "reset"

- Add "reboot" command as alias of "reset";
- Support command like: reboot loader/bootloader/recovery, etc.

Change-Id: I9748664aeca052a775a3f88f7fdf9b3923941026
Signed-off-by: Joseph Chen <chenjh@rock-chips.com>

cmd/boot.c

@@ -73,11 +73,17 @@ U_BOOT_CMD(
 #endif
 
 U_BOOT_CMD(
-        reset, 1, 0,    do_reset,
+        reset, 2, 0,    do_reset,
         "Perform RESET of the CPU",
         ""
 );
 
+U_BOOT_CMD(
+        reboot, 2, 0,    do_reset,
+        "Perform RESET of the CPU, alias of 'reset'",
+        ""
+);
+
 #ifdef CONFIG_CMD_POWEROFF
 U_BOOT_CMD(
 	poweroff, 1, 0,	do_poweroff,