r8169: change interrupt mask type to u32

RTL8125 uses a 32 bit interrupt mask even though only bits in the
lower 16 bits are used. Change interrupt mask size to u32 to be
prepared and reintroduce helper rtl_get_events.

Signed-off-by: Heiner Kallweit <hkallweit1@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>