staging: et131x: stop read when hit max delay in et131x_phy_mii_read

stop read and return error when hit max delay time.

Signed-off-by: Zhao, Gang <gamerh2o@gmail.com>
Acked-by: Mark Einon <mark.einon@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>