msm: mdss: swap flags for LP1 and LP2 modes

Use FB_BLANK_NORMAL flag for LP1 power mode and FB_BLANK_VSYNC_SUSPEND
flag for LP2 power mode. This better aligns with the definition of
these power modes since display updates are suspended in LP2 power
mode while updates can still occur in LP1 power mode.

Change-Id: Ica132e38dd1d0bb96368a1bbb51143100f0352cc
Signed-off-by: Aravind Venkateswaran <aravindh@codeaurora.org>