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/common/cmd_scsi.c b/common/cmd_scsi.c
index dd2c1ae..f89492f 100644
--- a/common/cmd_scsi.c
+++ b/common/cmd_scsi.c
@@ -623,11 +623,11 @@
 	"scsi device [dev] - show or set current device\n"
 	"scsi part [dev] - print partition table of one or all SCSI devices\n"
 	"scsi read addr blk# cnt - read `cnt' blocks starting at block `blk#'\n"
-	"     to memory address `addr'\n"
+	"     to memory address `addr'"
 );
 
 U_BOOT_CMD(
 	scsiboot, 3, 1, do_scsiboot,
 	"boot from SCSI device",
-	"loadAddr dev:part\n"
+	"loadAddr dev:part"
 );