net: rtl8139: Factor out hardware reset

net: rtl8139: Factor out hardware reset

This hardware reset and reset-wait implementation was twice in the
driver, factor it out into a separate function. This really should
use wait_for_bit() eventually and return -ETIMEDOUT, but thus far,
handling of any of this is missing from the driver. This must be
added later. Thus far, no functional change.

Signed-off-by: Marek Vasut <marek.vasut+renesas@gmail.com>
Cc: Joe Hershberger <joe.hershberger@ni.com>