msm: mdss: send DSI command using TPG when in secure session

Currently when secure display session is enabled, DSI
driver ignores DCS commands since it needs fetching of
data from none secure domain and it might lead to XPU
violation. Because of this panel health read fails which
leads to ESD detection failure and hence MDSS reset happens
during secure display session.
Fix this issue by sending DCS commands using
internal FIFO of DSI HW instead of fetching it from memory.

Change-Id: I825e2e4ae205bae36e813258c3aee95590c9d5af
Signed-off-by: Sandeep Panda <spanda@codeaurora.org>