clk: at91: clk-sam9x60-pll: fix return value check

sam9x60_frac_pll_compute_mul_frac() can't return zero. Remove the check
against zero to reflect this.

Fixes: 43b1bb4a9b ("clk: at91: clk-sam9x60-pll: re-factor to support plls with multiple outputs")
Reported-by: Dan Carpenter <error27@gmail.com>
Signed-off-by: Claudiu Beznea <claudiu.beznea@microchip.com>
Link: https://lore.kernel.org/r/20230227105931.2812412-1-claudiu.beznea@microchip.com
Signed-off-by: Stephen Boyd <sboyd@kernel.org>

drivers/clk/at91/clk-sam9x60-pll.c

@@ -668,7 +668,7 @@ sam9x60_clk_register_frac_pll(struct regmap *regmap, spinlock_t *lock,
 
 		ret = sam9x60_frac_pll_compute_mul_frac(&frac->core, FCORE_MIN,
 							parent_rate, true);
-		if (ret <= 0) {
+		if (ret < 0) {
 			hw = ERR_PTR(ret);
 			goto free;
 		}