core-utils: Replace usage of TARGET_PRODUCT with TARGET_BOARD_PLATFORM

For vendor_prop_context_restriction.mk

TARGET_PRODUCT is supposed to be used by OEMs not Chipset vendors,
So use TARGET_BOARD_PLATFORM instead of TARGET_PRODUCT.

Change-Id: I226bd330d00a7624a539b359ccf835d19e3d663d
CRs-Fixed: 2979907
1 file changed