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_doc.c b/common/cmd_doc.c
index 3385c67..5cc90f0 100644
--- a/common/cmd_doc.c
+++ b/common/cmd_doc.c
@@ -202,7 +202,7 @@
 	"doc write addr off size - read/write `size'"
 	" bytes starting at offset `off'\n"
 	"    to/from memory address `addr'\n"
-	"doc erase off size - erase `size' bytes of DOC from offset `off'\n"
+	"doc erase off size - erase `size' bytes of DOC from offset `off'"
 );
 
 int do_docboot (cmd_tbl_t *cmdtp, int flag, int argc, char *argv[])
@@ -342,7 +342,7 @@
 U_BOOT_CMD(
 	docboot,	4,	1,	do_docboot,
 	"boot from DOC device",
-	"loadAddr dev\n"
+	"loadAddr dev"
 );
 
 int doc_rw (struct DiskOnChip* this, int cmd,