media: chips-media: wave5: Fix Null reference while testing fluster

In the Linux kernel, the following vulnerability has been resolved: media: chips-media: wave5: Fix Null reference while testing fluster When multi instances are created/destroyed, many interrupts happens and structures for decoder are removed. "struct vpu_instance" this structure is shared for all flow in the decoder, so if the structure is not protected by lock, Null dereference could happens sometimes. IRQ Handler was spilt to two phases and Lock was added as well.