arm64: dts: apple: Add A11 devices

Add DTS files for the A11 SoC and the following devices based on it:

- iPhone 8
- iPhone 8 Plus
- iPhone X

On A11, Apple has introduced independent performance and efficiency core
clusters, so indicate it in the device tree as well.

Signed-off-by: Konrad Dybcio <konradybcio@kernel.org>
[Nick: SMP and m1n1 support, disabled SMC pinctrl]
Co-developed-by: Nick Chan <towinchenmi@gmail.com>
Signed-off-by: Nick Chan <towinchenmi@gmail.com>
Acked-by: Linus Walleij <linus.walleij@linaro.org>
Reviewed-by: Neal Gompa <neal@gompa.dev>
Signed-off-by: Hector Martin <marcan@marcan.st>