riscv-hw.c: match kernel type in syscall(). (#292)

syscall() doesn't care about these types at all, and the kernel uses cpu_set_t, so we're better off just removing the cast entirely.

src/riscv/linux/riscv-hw.c

diff --git a/src/riscv/linux/riscv-hw.c b/src/riscv/linux/riscv-hw.c
index d737aca..63a92e2 100644
--- a/src/riscv/linux/riscv-hw.c
+++ b/src/riscv/linux/riscv-hw.c
@@ -112,7 +112,7 @@
 	 *
 	 * for more details.
 	 */
-	int ret = syscall(NR_riscv_hwprobe, pairs, pairs_count, cpu_set_size, (unsigned long*)cpu_set, 0 /* flags */);
+	int ret = syscall(NR_riscv_hwprobe, pairs, pairs_count, cpu_set_size, cpu_set, 0 /* flags */);
 #else
 	int ret = __riscv_hwprobe(pairs, pairs_count, cpu_set_size, (unsigned long*)cpu_set, 0 /* flags */);
 #endif