drm/panfrost: Export all GPU feature registers

Midgard/Bifrost GPUs have a bunch of feature registers providing details
of what the hardware supports. Panfrost already reads these, this patch
exports them all to user space so that the jobs created by the user space
driver can be tuned for the particular hardware implementation.

Signed-off-by: Steven Price <steven.price@arm.com>
Reviewed-by: Alyssa Rosenzweig <alyssa.rosenzweig@collabora.com>
Signed-off-by: Rob Herring <robh@kernel.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20190724105626.53552-1-steven.price@arm.com