clk-bcm2835: Avoid null pointer exception

clk_desc_array[BCM2835_PLLB] doesn't exist so we dereference null when iterating

Signed-off-by: popcornmix <popcornmix@gmail.com>

drivers/clk/bcm/clk-bcm2835.c

@@ -2339,10 +2339,12 @@ static bool bcm2835_clk_is_claimed(const char *name)
 	int i;
 
 	for (i = 0; i < ARRAY_SIZE(clk_desc_array); i++) {
+		if (clk_desc_array[i].data) {
 			const char *clk_name = *(const char **)(clk_desc_array[i].data);
 			if (!strcmp(name, clk_name))
 				return bcm2835_clk_claimed[i];
 		}
+	}
 
 	return false;
 }