iommu/apple-dart: Write to all DART_T8020_STREAM_SELECT

We're about to add support for a DART variant that use more than 16
streams and requires writing to two separate stream select registers
when issuing TLB flushes.

Acked-by: Hector Martin <marcan@marcan.st>
Signed-off-by: Sven Peter <sven@svenpeter.dev>
Link: https://lore.kernel.org/r/20231126151701.16534-3-sven@svenpeter.dev


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