ARM: dts: msm: Add panel dimension details for Truly WVGA panel

Explicitly setting the physical dimensions of the panel helps
in correctly computing the DPI (dots per inch) settings. Add
this information for the Truly WVGA panel based on the data
provided in the panel specification.

Change-Id: Ie90ef896104b3f858f4e58f977cc5150d00312e9
Signed-off-by: Diego Wilson <dwilson@codeaurora.org>