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_fpga.c b/common/cmd_fpga.c
index 362bffd..2e017b8 100644
--- a/common/cmd_fpga.c
+++ b/common/cmd_fpga.c
@@ -357,9 +357,10 @@
 	    "\tload\tLoad device from memory buffer\n"
 	    "\tloadb\tLoad device from bitstream buffer (Xilinx devices only)\n"
 	    "\tloadmk\tLoad device generated with mkimage\n"
-	    "\tdump\tLoad device to memory buffer\n"
+	    "\tdump\tLoad device to memory buffer"
 #if defined(CONFIG_FIT)
+	    "\n"
 	    "\tFor loadmk operating on FIT format uImage address must include\n"
-	    "\tsubimage unit name in the form of addr:<subimg_uname>\n"
+	    "\tsubimage unit name in the form of addr:<subimg_uname>"
 #endif
 );