arm64: Kconfig: Update help text for CONFIG_ARCH_APPLE

Apple's A7-A11 SoC is now supported, so the original help text is no longer
accurate.

Acked-by: Krzysztof Kozlowski <krzk@kernel.org>
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>