drivers/{intel/wifi,wifi/generic}: Drop separate Intel WiFi driver

Currently, drivers/intel/wifi is a PCI driver (provides `struct
pci_driver`) as well as a chip driver (provides `struct
chip_operations`). However, there is no need for a separate chip
driver for the WiFi device since drivers/wifi/generic already provides
one.

Having two separate chip drivers makes it difficult to multi-source
WiFi devices and share the same firmware target without having to add
a probe property for each of these devices. This is unnecessary since
the WiFi driver in coreboot is primarily responsible for:
1. PCI resource allocation
2. ACPI SSDT node generation to expose wake property and SAR tables
3. SMBIOS table generation

For the most part, coreboot can perform the above operations without
really caring about the specifics of which WiFi device is being used
by the mainboard. Thus, this change drops the driver for intel/wifi
and moves the PCI driver support required for Intel WiFi chips into
drivers/wifi/generic. The PCI driver is retained for backward
compatibility with boards that never utilized the chip driver to
support Intel WiFi device. For these devices, the PCI driver helps
perform the same operations as above (except exposing the wake
property) by utilizing the same `wifi_generic_ops`.

This change also moves DRIVERS_INTEL_WIFI config to
wifi/generic/Kconfig.

BUG=b:169802515
BRANCH=zork

Change-Id: I780a7d1a87f387d5e01e6b35aac7cca31a2033ac
Signed-off-by: Furquan Shaikh <furquan@google.com>
---
D src/drivers/intel/wifi/Kconfig
D src/drivers/intel/wifi/Makefile.inc
D src/drivers/intel/wifi/chip.h
D src/drivers/intel/wifi/wifi.c
M src/drivers/wifi/generic/Kconfig
M src/drivers/wifi/generic/generic.c
6 files changed, 73 insertions(+), 167 deletions(-)