cmd: correct short text for tftpboot

The command's name is a misnomer.
The command loads a file but does not run (boot) it.

Signed-off-by: Heinrich Schuchardt <heinrich.schuchardt@canonical.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
diff --git a/cmd/Kconfig b/cmd/Kconfig
index 8ea064b..0e0be94 100644
--- a/cmd/Kconfig
+++ b/cmd/Kconfig
@@ -1719,7 +1719,7 @@
 	bool "tftpboot"
 	default y
 	help
-	  tftpboot - boot image via network using TFTP protocol
+	  tftpboot - load file via network using TFTP protocol
 
 config CMD_TFTPPUT
 	bool "tftp put"