regmap: irq: Fix possible ZERO_SIZE_PTR pointer dereferencing error.

Since we cannot make sure the 'chip->num_regs' will always be none zero
from the users, and then if 'chip->num_regs' equals to zero by mistake
or other reasons, the kzalloc() will return ZERO_SIZE_PTR, which equals
to ((void *)16).

So this patch fix this with just checking the 'chip->num_regs' before
calling kzalloc().

This also sorts the header files in alphabetical order at the same time.
Signed-off-by: Xiubo Li <Li.Xiubo@freescale.com>
Signed-off-by: Mark Brown <broonie@linaro.org>

drivers/base/regmap/regmap-irq.c

@@ -10,13 +10,13 @@
  * published by the Free Software Foundation.
  */
 
-#include <linux/export.h>
 #include <linux/device.h>
-#include <linux/regmap.h>
-#include <linux/irq.h>
+#include <linux/export.h>
 #include <linux/interrupt.h>
+#include <linux/irq.h>
 #include <linux/irqdomain.h>
 #include <linux/pm_runtime.h>
+#include <linux/regmap.h>
 #include <linux/slab.h>
 
 #include "internal.h"
@@ -347,6 +347,9 @@ int regmap_add_irq_chip(struct regmap *map, int irq, int irq_flags,
 	int ret = -ENOMEM;
 	u32 reg;
 
+	if (chip->num_regs <= 0)
+		return -EINVAL;
+
 	for (i = 0; i < chip->num_irqs; i++) {
 		if (chip->irqs[i].reg_offset % map->reg_stride)
 			return -EINVAL;