disp: rotator: add manager lock in wait4done

In wait4done manager lock is added to
sde_hw_rotator_free_rotctx so that it would not clear the
rotCtx of next commit handler if delayed in execution of
done handler happens.

Change-Id: I9a31d14267e7ec3ee30a21d577005ecdadae2d3c
Signed-off-by: Mahadevan <mahap@codeaurora.org>