iommu: apple-dart: Increase MAX_DARTS_PER_DEVICE to 3

ISP needs this.

Signed-off-by: Hector Martin <marcan@marcan.st>
Reviewed-by: Alyssa Rosenzweig <alyssa@rosenzweig.io>
Signed-off-by: Sasha Finkelstein <fnkl.kernel@gmail.com>
Reviewed-by: Sven Peter <sven@svenpeter.dev>
Link: https://lore.kernel.org/r/20250307-isp-dart-v3-1-684fe4489591@gmail.com


Signed-off-by: Joerg Roedel <jroedel@suse.de>