Autogenerate for mac and msu builtins

Created by: urekhun

Files changed:

• gcc/config/riscv/corev.md: update the builtins patterns.
• gcc/testsuite/gcc.target/riscv/cv-march-xcvmac-test-autogeneration-mac.c: test for autogeneration.
• gcc/testsuite/gcc.target/riscv/cv-march-xcvmac-test-autogeneration-msu.c: Likewise.