drm/msm/mdp5: Return error code in mdp5_pipe_release when deadlock is detected

In the Linux kernel, the following vulnerability has been resolved: drm/msm/mdp5: Return error code in mdp5_pipe_release when deadlock is detected mdp5_get_global_state runs the risk of hitting a -EDEADLK when acquiring the modeset lock, but currently mdp5_pipe_release doesn't check for if an error is returned. Because of this, there is a possibility of mdp5_pipe_release hitting a NULL dereference error. To avoid this, let's have mdp5_pipe_release check if mdp5_get_global_state returns an error and propogate that error. Changes since v1: - Separated declaration and initialization of *new_state to avoid compiler warning - Fixed some spelling mistakes in commit message Changes since v2: - Return 0 in case where hwpipe is NULL as this is considered normal behavior - Added 2nd patch in series to fix a similar NULL dereference issue in mdp5_mixer_release Patchwork: https://patchwork.freedesktop.org/patch/485179/