RISC-V: Add C intrinsic for Scalar Crypto Extension

This patch adds C intrinsics for Scalar Crypto Extension.

gcc/ChangeLog:

	* config.gcc: Include riscv_crypto.h.
	* config/riscv/riscv_crypto.h: New file.

gcc/testsuite/ChangeLog:

	* gcc.target/riscv/scalar_crypto_intrinsic-32.c: New test.
	* gcc.target/riscv/scalar_crypto_intrinsic-64.c: New test.