drm/imagination: Implement free list and HWRT create and destroy ioctls

Implement ioctls to create and destroy free lists and HWRT datasets. Free
lists are used for GPU-side memory allocation during geometry processing.
HWRT datasets are the FW-side structures representing render targets.

Changes since v8:
- Corrected license identifiers

Changes since v6:
- Fix out-of-bounds shift in get_cr_multisamplectl_val()

Changes since v4:
- Remove use of drm_gem_shmem_get_pages()

Changes since v3:
- Support free list grow requests from FW
- Use drm_dev_{enter,exit}

Co-developed-by: Boris Brezillon <boris.brezillon@collabora.com>
Signed-off-by: Boris Brezillon <boris.brezillon@collabora.com>
Co-developed-by: Donald Robson <donald.robson@imgtec.com>
Signed-off-by: Donald Robson <donald.robson@imgtec.com>
Signed-off-by: Sarah Walker <sarah.walker@imgtec.com>