vndk-def: Add (vndk-sp)? to fwk-only-rs matching

This commit adds (?:vndk-sp)? to FWK-ONLY-RS matching because some
targets have a copy of libft2.so in /system/lib[64]/vndk-sp but we still
want to treat it as FWK-ONLY-RS.

Bug: 37867089
Test: libft2.so is not labeled as vndk-sp-indirect in sailfish image.
Change-Id: Iad5db6417573f3e25bad5c027cb547d9df4be23a