mb/apple: Add MacBook Air 5,2 (A1466) support

What works:
- 4 GiB (Hynix RAM) model
- Linux 4.9, 5.10, 5.13
- SeaBIOS
- GRUB
- Tianocore
- Wi-Fi
- Bluetooth
- S3 suspend and resume
- Both USB ports
- Trackpad
- libgfxinit
- me_cleaner
- Speakers
- ACPI support for battery, AC, lid (lid wakeup also works)
- SD card reader
- Camera
- Mic
- usbdebug (USB port on the left side)
- Thunderbolt (probably works? see note below)

Known issues:
- Bad sound in headphones
- Not all memory configurations are supported

Payload issues:
- Keyboard doesn't work in GRUB if it was chainloaded from SeaBIOS.
  In SeaBIOS itself keyboard works.

- Thunderbolt
The thunderbolt-to-ethernet adapter is detected by the kernel:
    [  835.495393] thunderbolt 0-1: new device found, vendor=0x1
                   device=0x8003
    [  835.495408] thunderbolt 0-1: Apple, Inc. Thunderbolt to Gigabit
                   Ethernet Adapter
The network interface wasn't created though, so I couldn't test the
adapter. No idea if it's linux or coreboot, but I think it's linux issue.

Change-Id: I1ebe6f87a8254871698be74f913b9d969d722447
Signed-off-by: Evgeny Zinoviev <me@ch1p.io>
---
A Documentation/mainboard/apple/macbookair5_2.md
A Documentation/mainboard/apple/mba52_3v3.jpg
A Documentation/mainboard/apple/mba52_3v3_2.jpg
A Documentation/mainboard/apple/mba52_adapter.jpg
A Documentation/mainboard/apple/mba52_bat_unplug.jpg
A Documentation/mainboard/apple/mba52_motherboard.jpg
A Documentation/mainboard/apple/mba52_plug_j5100.jpg
M Documentation/mainboard/index.md
A src/mainboard/apple/macbookair5_2/Kconfig
A src/mainboard/apple/macbookair5_2/Kconfig.name
A src/mainboard/apple/macbookair5_2/Makefile.inc
A src/mainboard/apple/macbookair5_2/acpi/ec.asl
A src/mainboard/apple/macbookair5_2/acpi/platform.asl
A src/mainboard/apple/macbookair5_2/acpi/superio.asl
A src/mainboard/apple/macbookair5_2/acpi_tables.c
A src/mainboard/apple/macbookair5_2/board_info.txt
A src/mainboard/apple/macbookair5_2/cmos.default
A src/mainboard/apple/macbookair5_2/cmos.layout
A src/mainboard/apple/macbookair5_2/devicetree.cb
A src/mainboard/apple/macbookair5_2/dsdt.asl
A src/mainboard/apple/macbookair5_2/early_init.c
A src/mainboard/apple/macbookair5_2/gma-mainboard.ads
A src/mainboard/apple/macbookair5_2/gpio.c
A src/mainboard/apple/macbookair5_2/hda_verb.c
A src/mainboard/apple/macbookair5_2/mainboard.c
A src/mainboard/apple/macbookair5_2/spd/4g_hynix.spd.hex
A src/mainboard/apple/macbookair5_2/spd/4g_samsung.spd.hex
A src/mainboard/apple/macbookair5_2/spd/Makefile.inc
28 files changed, 830 insertions(+), 0 deletions(-)