clmul[h] instructions were added only for the ZBKC extension.
This patch includes them in the ZBC extension too.
Besides, added support of 'clmulr' instructions for ZBC extension.

gcc/ChangeLog:

     * config/riscv/bitmanip.md: Added clmulr instruction.
     * config/riscv/riscv-builtins.cc (AVAIL): Add new.
     * config/riscv/riscv.md: (UNSPEC_CLMULR): Add new unspec type.
     * config/riscv/riscv-cmo.def: Added built-in function for clmulr.
     * config/riscv/crypto.md: Move clmul[h] instructions to bitmanip.md.
     * config/riscv/riscv-scalar-crypto.def: Move clmul[h] built-in
functions to riscv-cmo.def.

gcc/testsuite/ChangeLog:

   * gcc.target/riscv/zbc32.c: New test.
   * gcc.target/riscv/zbc64.c: New test.