usf: Include usf_product.mk for USF PDK.

Bug: 237953890
Test: Compile pass. Verified sensor list & sampling on R4.
      The validation is done both on PDK build and tm-qpr-dev build.
Signed-off-by: Rick Chen <rickctchen@google.com>
Change-Id: Iff49dc63e1a3601dd254c292504aaf32dec79687
1 file changed