Command usage cleanup

Remove command name from all command "usage" fields and update
common/command.c to display "name - usage" instead of
just "usage". Also remove newlines from command usage fields.

Signed-off-by: Peter Tyser <ptyser@xes-inc.com>
diff --git a/common/cmd_setexpr.c b/common/cmd_setexpr.c
index 4125b18..9a5e720 100644
--- a/common/cmd_setexpr.c
+++ b/common/cmd_setexpr.c
@@ -63,7 +63,7 @@
 
 U_BOOT_CMD(
 	setexpr, 5, 0, do_setexpr,
-	"setexpr - set environment variable as the result of eval expression\n",
+	"set environment variable as the result of eval expression",
 	"name value1 <op> value2\n"
 	"    - set environment variable 'name' to the result of the evaluated\n"
 	"      express specified by <op>.  <op> can be &, |, ^, +, -, *, /, %\n"