net: rtl8169: add depends on PCI

The rtl8169 driver uses calls to dm_pci_bus_to_phys,
which are compiled under CONFIG_PCI.

Without CONFIG_PCI, this happens:

drivers/net/rtl8169.o: in function `rtl_recv_common':
drivers/net/rtl8169.c:555: undefined reference to `dm_pci_bus_to_phys'

It is only natural that this driver depends on CONFIG_PCI then.
The device does not work connected in another way anyway, and the driver
does not assume anything else at this moment.

Signed-off-by: Eugen Hristev <eugen.hristev@collabora.com>
Reviewed-by: Ramon Fried <rfried.dev@gmail.com>