RISC-V/testsuite: Fix comment termination in pr105314.c

Add terminating `/' character missing from one of the test harness
command clauses in pr105314.c.  This causes no issue with compilation
owing to another comment immediately following, but would cause a:

pr105314.c:3:1: warning: "/*" within comment [-Wcomment]

message if warnings were enabled.

	gcc/testsuite/
	* gcc.target/riscv/pr105314.c: Fix comment termination.