net: e1000: Depend on CONFIG_PCI

This driver depends on PCI. Update the Kconfig accordingly.

Signed-off-by: Sean Anderson <sean.anderson@seco.com>
Reviewed-by: Tim Harvey <tharvey@gateworks.com>
Reviewed-by: Stefan Roese <sr@denx.de>
Reviewed-by: Ramon Fried <rfried.dev@gmail.com>