panfrost/mfbd: Respect per-job depth write flag

panfrost/mfbd: Respect per-job depth write flag

While a depth buffer may be supplied, it only needs to be written to if
the depth writemask is set for any draw AND if the depth buffer is not
immediately invalidated (as is the case for scanout). This refactors
panfrost_job to provide a depth write requirement, which is now
implemented for MFBD depth buffers.

Signed-off-by: Alyssa Rosenzweig <alyssa@rosenzweig.io>