iommu/dart: APPLE_DART should depend on ARCH_APPLE

iommu/dart: APPLE_DART should depend on ARCH_APPLE

The Apple DART (Device Address Resolution Table) IOMMU is only present
on Apple ARM SoCs like the M1.  Hence add a dependency on ARCH_APPLE, to
prevent asking the user about this driver when configuring a kernel
without support for the Apple Silicon SoC family.

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Acked-by: Sven Peter <sven@svenpeter.dev>
Link: https://lore.kernel.org/r/44fcf525273b32c9afcd7e99acbd346d47f0e047.1628603162.git.geert+renesas@glider.be
Signed-off-by: Joerg Roedel <jroedel@suse.de>