drm/msm/dpu: move dpu_encoder's connector assignment to atomic_enable()

In the Linux kernel, the following vulnerability has been resolved: drm/msm/dpu: move dpu_encoder's connector assignment to atomic_enable() For cases where the crtc's connectors_changed was set without enable/active getting toggled , there is an atomic_enable() call followed by an atomic_disable() but without an atomic_mode_set(). This results in a NULL ptr access for the dpu_encoder_get_drm_fmt() call in the atomic_enable() as the dpu_encoder's connector was cleared in the atomic_disable() but not re-assigned as there was no atomic_mode_set() call. Fix the NULL ptr access by moving the assignment for atomic_enable() and also use drm_atomic_get_new_connector_for_encoder() to get the connector from the atomic_state. Patchwork: https://patchwork.freedesktop.org/patch/606729/