Update Android.bp to use vendor property.

All modules in v4l2_codec2 is vendor modules. This CL changes to use
"vendor" property instead of "vendor_available" or "soc_specific".

Note: "vendor_available" property means a module could be depended
by both system and vendor modules.
"soc_specific" property means a module is specific to an certain SoC.

Bug: 153403351
Test: m -j32

Change-Id: Ia719fc0e0c623bb8f2fc5578a75646b26c5f0771