msm: mdss: fb: fix mismatch between current videomode and modelist

When multiple panel timings are available and enumerating video mode
list, the configuration present in the modelist may differ from the
actual configuration in fb variable info. This may cause issues when
usermode does GET_VSCREENINFO/PUT_VSCREENINFO calls. Fix this by
updating variable info with current timing mode.

Change-Id: Id9d4068bdb4851ffb4bc7e218a0666d1bd64eebe
Signed-off-by: Adrian Salido-Moreno <adrianm@codeaurora.org>
Signed-off-by: Veera Sundaram Sankaran <veeras@codeaurora.org>