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_net.c b/common/cmd_net.c
index 92bbf85..68183c4 100644
--- a/common/cmd_net.c
+++ b/common/cmd_net.c
@@ -40,7 +40,7 @@
 U_BOOT_CMD(
 	bootp,	3,	1,	do_bootp,
 	"boot image via network using BOOTP/TFTP protocol",
-	"[loadAddress] [[hostIPaddr:]bootfilename]\n"
+	"[loadAddress] [[hostIPaddr:]bootfilename]"
 );
 
 int do_tftpb (cmd_tbl_t *cmdtp, int flag, int argc, char *argv[])
@@ -51,7 +51,7 @@
 U_BOOT_CMD(
 	tftpboot,	3,	1,	do_tftpb,
 	"boot image via network using TFTP protocol",
-	"[loadAddress] [[hostIPaddr:]bootfilename]\n"
+	"[loadAddress] [[hostIPaddr:]bootfilename]"
 );
 
 int do_rarpb (cmd_tbl_t *cmdtp, int flag, int argc, char *argv[])
@@ -62,7 +62,7 @@
 U_BOOT_CMD(
 	rarpboot,	3,	1,	do_rarpb,
 	"boot image via network using RARP/TFTP protocol",
-	"[loadAddress] [[hostIPaddr:]bootfilename]\n"
+	"[loadAddress] [[hostIPaddr:]bootfilename]"
 );
 
 #if defined(CONFIG_CMD_DHCP)
@@ -74,7 +74,7 @@
 U_BOOT_CMD(
 	dhcp,	3,	1,	do_dhcp,
 	"boot image via network using DHCP/TFTP protocol",
-	"[loadAddress] [[hostIPaddr:]bootfilename]\n"
+	"[loadAddress] [[hostIPaddr:]bootfilename]"
 );
 #endif
 
@@ -87,7 +87,7 @@
 U_BOOT_CMD(
 	nfs,	3,	1,	do_nfs,
 	"boot image via network using NFS protocol",
-	"[loadAddress] [[hostIPaddr:]bootfilename]\n"
+	"[loadAddress] [[hostIPaddr:]bootfilename]"
 );
 #endif
 
@@ -269,7 +269,7 @@
 U_BOOT_CMD(
 	ping,	2,	1,	do_ping,
 	"send ICMP ECHO_REQUEST to network host",
-	"pingAddress\n"
+	"pingAddress"
 );
 #endif