cmd: bootefi: cosmetic

Short help (description) in bootefi command has a trailing "\n" that
breaks the "help" command output (empty line after "bootefi").

Nothing important, doesn't affect anything but better be fixed in the
upcoming release.

Still working on i.MX6 and their siblings NAND U-Boot update -- it
works here but not ready for a submission yet. Anyway it is for the
next cycle, not going to go into this release because it is too big
and may affect something else.

Also have some thoughts about fastboot (using multiple devices) but
this will go into separate email with RFC.
Signed-off-by: NSergey Kubushyn <ksi@koi8.net>

cmd/bootefi.c

@@ -255,7 +255,7 @@ static char bootefi_help_text[] =
 
 U_BOOT_CMD(
 	bootefi, 3, 0, do_bootefi,
-	"Boots an EFI payload from memory\n",
+	"Boots an EFI payload from memory",
 	bootefi_help_text
 );