mdss: dsi: Fix null dereferences

Fix potential null dereferences in driver.

Change-Id: Idd8d4eb16bb1b9562da1f5225d91cf90d8230bfe
Signed-off-by: Charles Bin <cbin@codeaurora.org>
msm: mdss: Check ctl power on status before BTA status check

Control path power on status should be checked before BTA status
check else command sending failure and IOMMU page faults during
bootup can be observed if ESD is enabled for device. Currently
IOMMU is not powered on when commands are being sent.

Change-Id: Ice66f38e79755eb14843fc63afe058e4bab2f0e2
Signed-off-by: Jayant Shekhar <jshekhar@codeaurora.org>
Signed-off-by: Xiaoming Zhou <zhoux@codeaurora.org>
Signed-off-by: Anusha Koduru <kanusha@codeaurora.org>
msm: mdss: Wait for vsync before iommu attach during cont splash

During first borderfill commit in splash cleanup, wait for vsync
before iommu attach to prevent IOMMU page faults during bootup.

Change-Id: I68b7162d090513b082cbd4c0013731cedc0ebdbe
Signed-off-by: Jayant Shekhar <jshekhar@codeaurora.org>
Signed-off-by: Vineet Bajaj <vbajaj@codeaurora.org>
Signed-off-by: Anusha Koduru <kanusha@codeaurora.org>