RISC-V: Fix one typo in .SAT_TRUNC test func name [NFC]

Fix one typo `sat_truc` to `sat_trunc`, as well as `SAT_TRUC` to `SAT_TRUNC`.

gcc/testsuite/ChangeLog:

	* gcc.target/riscv/sat_arith.h: Fix SAT_TRUNC typo.
	* gcc.target/riscv/sat_u_trunc-1.c: Ditto.
	* gcc.target/riscv/sat_u_trunc-13.c: Ditto.
	* gcc.target/riscv/sat_u_trunc-14.c: Ditto.
	* gcc.target/riscv/sat_u_trunc-15.c: Ditto.
	* gcc.target/riscv/sat_u_trunc-2.c: Ditto.
	* gcc.target/riscv/sat_u_trunc-3.c: Ditto.
	* gcc.target/riscv/sat_u_trunc-4.c: Ditto.
	* gcc.target/riscv/sat_u_trunc-5.c: Ditto.
	* gcc.target/riscv/sat_u_trunc-6.c: Ditto.
	* gcc.target/riscv/sat_u_trunc-7.c: Ditto.
	* gcc.target/riscv/sat_u_trunc-8.c: Ditto.
	* gcc.target/riscv/sat_u_trunc-9.c: Ditto.
	* gcc.target/riscv/sat_u_trunc-run-1.c: Ditto.
	* gcc.target/riscv/sat_u_trunc-run-13.c: Ditto.
	* gcc.target/riscv/sat_u_trunc-run-14.c: Ditto.
	* gcc.target/riscv/sat_u_trunc-run-15.c: Ditto.
	* gcc.target/riscv/sat_u_trunc-run-2.c: Ditto.
	* gcc.target/riscv/sat_u_trunc-run-3.c: Ditto.
	* gcc.target/riscv/sat_u_trunc-run-4.c: Ditto.
	* gcc.target/riscv/sat_u_trunc-run-5.c: Ditto.
	* gcc.target/riscv/sat_u_trunc-run-6.c: Ditto.
	* gcc.target/riscv/sat_u_trunc-run-7.c: Ditto.
	* gcc.target/riscv/sat_u_trunc-run-8.c: Ditto.
	* gcc.target/riscv/sat_u_trunc-run-9.c: Ditto.

Signed-off-by: Pan Li <pan2.li@intel.com>