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/trizepsiv/eeprom.c b/board/trizepsiv/eeprom.c
index 9fa7aef..b6b16bf 100644
--- a/board/trizepsiv/eeprom.c
+++ b/board/trizepsiv/eeprom.c
@@ -81,4 +81,5 @@
 	"\tdm9000ee read \n"
 	"\tword:\t\t00-02 : MAC Address\n"
 	"\t\t\t03-07 : DM9000 Configuration\n"
-	"\t\t\t08-63 : User data\n");
+	"\t\t\t08-63 : User data"
+);