v3dv/descriptor_set: don't free individual set if not allowed

v3dv/descriptor_set: don't free individual set if not allowed

If we have a host_memory_base pointer it means that we are handling
the pool memory as a whole, so each set is a sub-slice of the memory
pool. In this case we can't just free the individual set. In other
words, VK_DESCRIPTOR_POOL_CREATE_FREE_DESCRIPTOR_SET_BIT is not set.

Note tha at that point we were able to sub-allocate an set, and we are
failing to sub-allocate the pool bo for the descripto bo. So
technically we could try to return that set to the pool (so undo the
change on host_memory_ptr before), that I assume was my intention when
(wrongly) calling vk_free there. But in practice, at that point we are
already on a out of descriptor pool situation, so in the end it
doesn't even matter.

This fixes a double free crash with the UE4 VehicleGame demo.

Reviewed-by: Iago Toral Quiroga <itoral@igalia.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/9640>