General help message cleanup

Many of the help messages were not really helpful; for example, many
commands that take no arguments would not print a correct synopsis
line, but "No additional help available." which is not exactly wrong,
but not helpful either.

Commit ``Make "usage" messages more helpful.'' changed this
partially. But it also became clear that lots of "Usage" and "Help"
messages (fields "usage" and "help" in struct cmd_tbl_s respective)
were actually redundant.

This patch cleans this up - for example:

Before:
	=> help dtt
	dtt - Digital Thermometer and Thermostat

	Usage:
	dtt         - Read temperature from digital thermometer and thermostat.

After:
	=> help dtt
	dtt - Read temperature from Digital Thermometer and Thermostat

	Usage:
	dtt

Signed-off-by: Wolfgang Denk <wd@denx.de>
diff --git a/board/amcc/taihu/lcd.c b/board/amcc/taihu/lcd.c
index 6b68f33..c3dc983 100644
--- a/board/amcc/taihu/lcd.c
+++ b/board/amcc/taihu/lcd.c
@@ -233,25 +233,25 @@
 U_BOOT_CMD(
 	lcd_cls, 1, 1, do_lcd_clear,
 	"lcd clear display",
-	NULL
-	);
+	""
+);
 
 U_BOOT_CMD(
 	lcd_puts, 2, 1, do_lcd_puts,
 	"display string on lcd",
-	"<string> - <string> to be displayed\n"
-	);
+	"<string> - <string> to be displayed"
+);
 
 U_BOOT_CMD(
 	lcd_putc, 2, 1, do_lcd_putc,
 	"display char on lcd",
-	"<char> - <char> to be displayed\n"
-	);
+	"<char> - <char> to be displayed"
+);
 
 U_BOOT_CMD(
 	lcd_cur, 3, 1, do_lcd_cur,
 	"shift cursor on lcd",
 	"<count> <dir> - shift cursor on lcd <count> times, direction is <dir> \n"
 	" <count> - 0..31\n"
-	" <dir>   - 0=backward 1=forward\n"
-	);
+	" <dir>   - 0=backward 1=forward"
+);
diff --git a/board/amcc/taihu/taihu.c b/board/amcc/taihu/taihu.c
index 669429b..d8806ac 100644
--- a/board/amcc/taihu/taihu.c
+++ b/board/amcc/taihu/taihu.c
@@ -94,8 +94,8 @@
 U_BOOT_CMD (
 	sw2_stat, 1, 1, do_sw_stat,
 	"show status of switch 2",
-	NULL
-	);
+	""
+);
 
 static int do_led_ctl(cmd_tbl_t* cmd_tp, int flags, int argc, char *argv[])
 {
@@ -134,8 +134,8 @@
 	led_ctl, 3, 1, do_led_ctl,
 	"make led 1 or 2  on or off",
 	"<led_no> <on/off>	-  make led <led_no> on/off,\n"
-	"\tled_no is 1 or 2\t"
-	);
+	"\tled_no is 1 or 2"
+);
 
 #define SPI_CS_GPIO0	0
 #define SPI_SCLK_GPIO14	14
diff --git a/board/amcc/taihu/update.c b/board/amcc/taihu/update.c
index 8e96905..f9c31b3 100644
--- a/board/amcc/taihu/update.c
+++ b/board/amcc/taihu/update.c
@@ -128,5 +128,5 @@
 U_BOOT_CMD (
 	update_boot_eeprom, 1, 1, update_boot_eeprom,
 	"update boot eeprom content",
-	NULL
-	);
+	""
+);