msm: mdss: fix typo checking the wrong context for error handling

Fix typo during the off work item; this can cause that
in case of an failure in the driver, the error goes silent
and power resources for the second display context
(i.e. bandwidth and clocks) stay enabled when not needed
without warning for this error.

Change-Id: Iff2683356ef6391ae57b3c5b711b544003584c7c
Signed-off-by: Ingrid Gallardo <ingridg@codeaurora.org>