msm: mdss: update the PHY settings for DSI1 for 8939

For 8939, the DSI_1_PHY_DSIPHY_GLBL_TEST_CTRL register setting
is different when compared to other chipsets. Update the
register settings for this based on the DSI_HW_VERSION check.
This enables dual DSI panel support on 8939.

Change-Id: Iebf8015d4a4c978283e74b104bd955a6bf7004c2
Signed-off-by: Padmanabhan Komanduru <pkomandu@codeaurora.org>