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/acadia/cmd_acadia.c b/board/amcc/acadia/cmd_acadia.c
index d47cf1a..c427f9e 100644
--- a/board/amcc/acadia/cmd_acadia.c
+++ b/board/amcc/acadia/cmd_acadia.c
@@ -97,5 +97,5 @@
 U_BOOT_CMD(
 	bootstrap,	3,	0,	do_bootstrap,
 	"program the I2C bootstrap EEPROM",
-	"<cpu-freq> <nor|nand> - program the I2C bootstrap EEPROM\n"
-	);
+	"<cpu-freq> <nor|nand> - program the I2C bootstrap EEPROM"
+);