msm: ultrasound: add support for various msm families

Various msm families have differences in interface with QDSP6.
To support these differences some updates in the ultrasound framework's
source files hierarchy are required.
Ultrasound related interface with QDSP6 for msm family
is implemented in dedicated files; the proper directory,
including the files, is selected during the kernel build.

Change-Id: Ic60f5822670e5c511f997e34f9530fb87cc32d62
Signed-off-by: Baruch Eruchimovitch <baruche@codeaurora.org>