sys/linux: Add description for Mali Panthor driver

[lzapolskas]

Add the descriptions for the Panthor Mali GPU driver ioctl interface, using the latest definitions from https://cgit.freedesktop.org/drm/drm-misc/tree/include/uapi/drm/panthor_drm.h.

[google-cla]

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[a-nogikh]

Thanks!
Please address cla/gooogle and ci / aux:

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