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

What works:
- 4 GiB (Hynix RAM) model
- Linux 4.9, Linux 5.10
- SeaBIOS
- GRUB
- Tianocore
- Wi-Fi
- 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)

Not tested:
- Thunderbolt

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

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, 841 insertions(+), 0 deletions(-)