testsuite, riscv: fix broken dg directives

testsuite, riscv: fix broken dg directives

Found by dg-lint.

gcc/testsuite/ChangeLog:
	* gcc.target/riscv/cmo-zicbop-1.c: Fix missing space before
	trailing } in dg-do directive.
	* gcc.target/riscv/cmo-zicbop-2.c: Likewise.
	* gcc.target/riscv/prefetch-zicbop.c: Likewise.
	* gcc.target/riscv/prefetch-zihintntl.c: Likewise.