cmd: fix tftpput command

Calling tftpput with less than 2 arguments must lead to a failure.

If tftpput is called with two arguments, these are the address and
the size of the file to be transferred.

Signed-off-by: Heinrich Schuchardt <heinrich.schuchardt@canonical.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
1 file changed