msm: mdss: Fix dynamic refresh sequence

Dynamic refresh done interrupt is received and it is cleared.
Unmasking of PLL_UNLOCKED interrupt should be done only after
checking if RESETSM_READY_STATUS.CORE_READY is 1. This would
ensure that the clocks are in proper state before PLL_UNLOCKED
interrupt is unmasked.

Change-Id: I5d5762fada1a0722d0eb71fd9006d14e847ca388
Signed-off-by: Ashish Garg <ashigarg@codeaurora.org>