r8169: add helper rtl_wait_txrx_fifo_empty

Add a helper for waiting for FIFO's to be empty, again the name is
borrowed from the vendor driver.

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