rslib: Make some functions static

Fix sparse warnings:

lib/reed_solomon/test_rslib.c:313:5: warning: symbol 'ex_rs_helper' was not declared. Should it be static?
lib/reed_solomon/test_rslib.c:349:5: warning: symbol 'exercise_rs' was not declared. Should it be static?
lib/reed_solomon/test_rslib.c:407:5: warning: symbol 'exercise_rs_bc' was not declared. Should it be static?
Reported-by: Hulk Robot <hulkci@huawei.com>
Signed-off-by: YueHaibing <yuehaibing@huawei.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: <ferdinand.blomqvist@gmail.com>
Link: https://lkml.kernel.org/r/20190702061847.26060-1-yuehaibing@huawei.com

lib/reed_solomon/test_rslib.c

@@ -310,7 +310,7 @@ static void test_uc(struct rs_control *rs, int len, int errs,
 	stat->nwords += trials;
 }
 
-int ex_rs_helper(struct rs_control *rs, struct wspace *ws,
+static int ex_rs_helper(struct rs_control *rs, struct wspace *ws,
 			int len, int trials, int method)
 {
 	static const char * const desc[] = {
@@ -346,7 +346,7 @@ int ex_rs_helper(struct rs_control *rs, struct wspace *ws,
 	return retval;
 }
 
-int exercise_rs(struct rs_control *rs, struct wspace *ws,
+static int exercise_rs(struct rs_control *rs, struct wspace *ws,
 		       int len, int trials)
 {
 
@@ -404,7 +404,7 @@ static void test_bc(struct rs_control *rs, int len, int errs,
 	stat->nwords += trials;
 }
 
-int exercise_rs_bc(struct rs_control *rs, struct wspace *ws,
+static int exercise_rs_bc(struct rs_control *rs, struct wspace *ws,
 			  int len, int trials)
 {
 	struct bcstat stat = {0, 0, 0, 0};