drm/panthor: Convert IOCTL defines to an enum

Use an enum instead of #defines for panthor IOCTLs. This allows the
header to be used with Rust code as bindgen can't handle complex
defines.

Cc: Beata Michalska <beata.michalska@arm.com>
Signed-off-by: Rob Herring (Arm) <robh@kernel.org>
Reviewed-by: Alice Ryhl <aliceryhl@google.com>
Acked-by: Boris Brezillon <boris.brezillon@collabora.com>
Reviewed-by: Steven Price <steven.price@arm.com>
Signed-off-by: Boris Brezillon <boris.brezillon@collabora.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20250204232824.3819437-1-robh@kernel.org