clk: fix incorrect usage of ENOSYS

ENOSYS is special and should only be used for incorrect syscall number.
It does not seem to be the case here.

Reported by checkpatch.pl while working on clock protection.
Acked-by: NLinus Walleij <linus.walleij@linaro.org>
Tested-by: NQuentin Schulz <quentin.schulz@free-electrons.com>
Tested-by: NMaxime Ripard <maxime.ripard@free-electrons.com>
Acked-by: NMichael Turquette <mturquette@baylibre.com>
Signed-off-by: NJerome Brunet <jbrunet@baylibre.com>
Signed-off-by: NMichael Turquette <mturquette@baylibre.com>
Link: lkml.kernel.org/r/20171201215200.23523-2-jbrunet@baylibre.com

drivers/clk/clk.c

@@ -1888,7 +1888,7 @@ static int clk_core_set_parent(struct clk_core *core, struct clk_core *parent)
 
 	/* verify ops for for multi-parent clks */
 	if ((core->num_parents > 1) && (!core->ops->set_parent)) {
-		ret = -ENOSYS;
+		ret = -EPERM;
 		goto out;
 	}