fix [3312683] Camera mirroring problem after switching from back to front camera

the crop as well as buffer orientation can change at every frame, when that happens
we need to reset the hwc HAL (ie: set the GEOMETRY_CHANGED flag).
currently we achieve this by taking the same code path than an actual geometry change
which is a bit more heavy than necessary.

Change-Id: I751f9ed1eeec0c27db7df2e77d5d17c6bcc17a24