drm/panthor: Add support for Mali-Gx20 and Mali-Gx25 GPUs

This patch adds firmware binary and GPU model naming support for
Mali-Gx20 and Mali-Gx25 GPUs.

Reviewed-by: Steven Price <steven.price@arm.com>
Reviewed-by: Liviu Dudau <liviu.dudau@arm.com>
Signed-off-by: Karunika Choo <karunika.choo@arm.com>
Signed-off-by: Steven Price <steven.price@arm.com>
Link: https://lore.kernel.org/r/20250807162633.3666310-8-karunika.choo@arm.com