doubleshot: adding legacy msm camera driver for doubleshot

Fixes doubleshot camera issues (exiting hangs, restart hangs).
Should work fine front/back, video (except 1080p for some
reason doesn't work).

It's packed with MACH_DOUBLESHOT ifs, so it won't collide
with common camera drivers.

Change-Id: I93a8951db1ef11aa98e590679f93ff1f9ca0b289