RISC-V: Add builtin .def file dependencies

riscv-builtins.cc includes riscv-cmo.def and riscv-scalar-crypto.def
(making dependencies) but their dependencies must be explicitly defined at
the configuration file, t-riscv.

They were the last two .def files without correct dependency information.

gcc/ChangeLog:

	* config/riscv/t-riscv: Add dependencies for riscv-builtins.cc,
	riscv-cmo.def and riscv-scalar-crypto.def.