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_ext2.c b/common/cmd_ext2.c
index 923b355..6ee60c6 100644
--- a/common/cmd_ext2.c
+++ b/common/cmd_ext2.c
@@ -118,7 +118,7 @@
 	ext2ls,	4,	1,	do_ext2ls,
 	"list files in a directory (default /)",
 	"<interface> <dev[:part]> [directory]\n"
-	"    - list files from 'dev' on 'interface' in a 'directory'\n"
+	"    - list files from 'dev' on 'interface' in a 'directory'"
 );
 
 /******************************************************************************
@@ -256,5 +256,5 @@
 	"load binary file from a Ext2 filesystem",
 	"<interface> <dev[:part]> [addr] [filename] [bytes]\n"
 	"    - load binary file 'filename' from 'dev' on 'interface'\n"
-	"      to address 'addr' from ext2 filesystem\n"
+	"      to address 'addr' from ext2 filesystem"
 );