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_display.c

@@ -0,0 +1,54 @@
+/*
+ * (C) Copyright 2005
+ * Wolfgang Denk, DENX Software Engineering, wd@denx.de.
+ *
+ * SPDX-License-Identifier:	GPL-2.0+
+ */
+
+#include <common.h>
+#include <command.h>
+#include <led-display.h>
+
+#undef DEBUG_DISP
+
+int do_display (cmd_tbl_t *cmdtp, int flag, int argc, char * const argv[])
+{
+	int i;
+
+	/* Clear display */
+	display_set(DISPLAY_CLEAR | DISPLAY_HOME);
+
+	if (argc < 2)
+		return (0);
+
+	for (i = 1; i < argc; i++) {
+		char *p = argv[i];
+
+		if (i > 1) { /* Insert a space between strings */
+			display_putc(' ');
+		}
+
+		while ((*p)) {
+#ifdef DEBUG_DISP
+			putc(*p);
+#endif
+			display_putc(*p++);
+		}
+	}
+
+#ifdef DEBUG_DISP
+	putc('\n');
+#endif
+
+	return (0);
+}
+
+/***************************************************/
+
+U_BOOT_CMD(
+	display,	CONFIG_SYS_MAXARGS,	1,	do_display,
+	"display string on dot matrix display",
+	"[<string>]\n"
+	"    - with <string> argument: display <string> on dot matrix display\n"
+	"    - without arguments: clear dot matrix display"
+);