panfrost: Expose serialized NIR support

Serialized NIR is required for clover with the SPIR-V pipeline. With
this change and PAN_MESA_DEBUG=deqp, clinfo is able to successfully
probe panfrost.

Code from Nouveau (commit 7955fabc by
Karol Herbst).

Signed-off-by: Alyssa Rosenzweig <alyssa.rosenzweig@collabora.com>
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merge request