Mark functions as static

Mark functions used only in the same translation unit as static. This
only includes functions that do not have a prototype in a header file
either.

Reviewed-by: Ryan Moeller <ryan@iXsystems.com>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Arvind Sankar <nivedita@alum.mit.edu>
Closes #10470

cmd/raidz_test/raidz_bench.c

@@ -113,7 +113,7 @@ run_gen_bench_impl(const char *impl)
 	}
 }
 
-void
+static void
 run_gen_bench(void)
 {
 	char **impl_name;
@@ -197,7 +197,7 @@ run_rec_bench_impl(const char *impl)
 	}
 }
 
-void
+static void
 run_rec_bench(void)
 {
 	char **impl_name;