mdss: display: move mdss_mdp_irq_enable out of clk_lock scope

There are potential deadlock between irq handler and
mdss_mdp_irq_enable() since both can acquire mdss_lock
before trying to grab local lock. Add koff_lock for kickoff
related function in addition to original clk_lock which used
for clock related function to reduce unnecessary lock contention.

CRs-Fixed: 665524
Change-Id: Iebc5023eb9dc99f2a2709379bfac67ec275046a7
Signed-off-by: Kuogee Hsieh <khsieh@codeaurora.org>