r8169: add helper r8168g_wait_ll_share_fifo_ready

Create a helper for this waiting function, name of the helper is
borrowed from the vendor driver. In addition don't return in the two
hw_init functions if the first wait runs into a timeout, there's no
benefit in doing so.

Signed-off-by: Heiner Kallweit <hkallweit1@gmail.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>