r8169: enforce RX_MULTI_EN on rtl8168ep/8111ep chips

Enforcing this flag in RxConfig for the mentioned chips fixes netdev
watchdog issues prepended with AMD IOMMU message(s) like:
AMD-Vi: Event logged [IO_PAGE_FAULT device=01:00.0 domain=0x001d address=0x0000000000003000 flags=0x0050]

Note that this flag is also set in Realtek's own driver for these chips.

Signed-off-by: Ivan Vecera <ivecera@redhat.com>
Tested-by: Alexander Lindqvist <alexander@bitspace.se>
Acked-by: Francois Romieu <romieu@fr.zoreil.com>
Signed-off-by: David S. Miller <davem@davemloft.net>