isl_tab_rollback: restore rows that are no longer marked redundant
isl_tab_rollback: restore rows that are no longer marked redundant

When a row is marked redundant, it may have a negative (but strictly
larger than -1) sample value.  When undoing this marking, we need
to make sure the sample value is restored to a non-negative value.

UBERTC/isl,Distrotech/isl,jleben/isl,simbuerg/isl,serge-sans-paille/isl,serge-sans-paille/isl,inducer/isl-mirror,serge-sans-paille/isl,abduld/isl,KangDroidSMProject/ISL,pierrotdelalune/isl,cfx-next/toolchain_isl-upstream,Meinersbur/isl,inducer/isl-mirror,inducer/isl-mirror,UBERTC/isl,nicolasvasilache/isl,nicolasvasilache/isl,Distrotech/isl,KangDroidSMProject/ISL,jleben/isl,crossbuild/isl,jleben/isl,simbuerg/isl,epowers/isl,cfx-next/toolchain_isl-upstream,epowers/isl,evaautomation/isl,UBERTC/isl,simbuerg/isl,SaberMod/isl-current,evaautomation/isl,BobSaget-Mod/libisl,PollyLabs/isl,BobSaget-Mod/libisl,Distrotech/isl,PollyLabs/isl,KangDroidSMProject/ISL,BobSaget-Mod/libisl,BenzoSM/isl,VanirLLVM/toolchain_isl,jleben/isl,PollyLabs/isl,VanirLLVM/toolchain_isl,nicolasvasilache/isl,epowers/isl,BenzoSM/isl,KangDroidSMProject/ISL,BobSaget-Mod/libisl,pierrotdelalune/isl,Meinersbur/isl,abduld/isl,BenzoSM/isl,nicolasvasilache/isl,nicolasvasilache/isl,evaautomation/isl,simbuerg/isl,tobig/isl,epowers/isl,serge-sans-paille/isl,pierrotdelalune/isl,crossbuild/isl,cfx-next/toolchain_isl-upstream,BobSaget-Mod/libisl,VanirLLVM/toolchain_isl,pierrotdelalune/isl,cfx-next/toolchain_isl-upstream,SaberMod/isl-current,pierrotdelalune/isl,abduld/isl,PollyLabs/isl,cfx-next/toolchain_isl-upstream,SaberMod/isl-current,Meinersbur/isl,crossbuild/isl,KangDroidSMProject/ISL,jleben/isl,tobig/isl,SaberMod/isl-current,PollyLabs/isl,crossbuild/isl,tobig/isl,tobig/isl,Distrotech/isl,Meinersbur/isl,inducer/isl-mirror,abduld/isl,simbuerg/isl,BenzoSM/isl,Distrotech/isl,VanirLLVM/toolchain_isl,VanirLLVM/toolchain_isl,inducer/isl-mirror,evaautomation/isl,UBERTC/isl,BenzoSM/isl,epowers/isl,serge-sans-paille/isl