staging: et131x: Simplify for loop in et131x_init_send()

The for loop in this function increments two variables and has an unusual
starting index of 1 (not 0). Make it look more familiar.

Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Mark Einon <mark.einon@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>