Move all command code into its own directory

There are a lot of unrelated files in common, including all of the commands.
Moving them into their own directory makes them easier to find and is more
logical.

Some commands include non-command code, such as cmd_scsi.c. This should be
sorted out at some point so that the function can be enabled with or without
the associated command.

Unfortunately, with m68k I get this error:

m68k:  +   M5329AFEE
+arch/m68k/cpu/mcf532x/start.o: In function `_start':
+arch/m68k/cpu/mcf532x/start.S:159:(.text+0x452): relocation truncated to fit: R_68K_PC16 against symbol `board_init_f' defined in .text.board_init_f section in common/built-in.o

I hope someone can shed some light on what this means. I hope it isn't
depending on the position of code in the image.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>
Reviewed-by: Heiko Schocher <hs@denx.de>
Acked-by: Stefan Roese <sr@denx.de>
Acked-by: Przemyslaw Marczak <p.marczak@samsung.com>

cmd/cmd_irq.c

@@ -0,0 +1,40 @@
+/*
+ * Copyright 2008 Freescale Semiconductor, Inc.
+ *
+ * SPDX-License-Identifier:	GPL-2.0+
+ */
+
+#include <common.h>
+#include <config.h>
+#include <command.h>
+
+static int do_interrupts(cmd_tbl_t *cmdtp, int flag, int argc,
+			 char * const argv[])
+{
+
+	if (argc != 2)
+		return CMD_RET_USAGE;
+
+	/* on */
+	if (strncmp(argv[1], "on", 2) == 0)
+		enable_interrupts();
+	else
+		disable_interrupts();
+
+	return 0;
+}
+
+U_BOOT_CMD(
+	interrupts, 5, 0, do_interrupts,
+	"enable or disable interrupts",
+	"[on, off]"
+);
+
+/* Implemented in $(CPU)/interrupts.c */
+int do_irqinfo (cmd_tbl_t *cmdtp, int flag, int argc, char * const argv[]);
+
+U_BOOT_CMD(
+	irqinfo,    1,    1,     do_irqinfo,
+	"print information about IRQs",
+	""
+);