Don't build Gallery2 when building LegacyCamera

LegacyCamera can't be built into the new Gallery2 app
We will use the MR0 Gallery2 instead named LegacyGallery2

Signed-off-by: Michael Bestas <mikeioannina@gmail.com>

Change-Id: I6d555e733cefab8b010428b9fff8da92b7fa3058