drm/msm/a6xx: Fix refcount leak in a6xx_gpu_init

In the Linux kernel, the following vulnerability has been resolved: drm/msm/a6xx: Fix refcount leak in a6xx_gpu_init of_parse_phandle() returns a node pointer with refcount incremented, we should use of_node_put() on it when not need anymore. a6xx_gmu_init() passes the node to of_find_device_by_node() and of_dma_configure(), of_find_device_by_node() will takes its reference, of_dma_configure() doesn't need the node after usage. Add missing of_node_put() to avoid refcount leak.