net: usb: Use kstrtobool() instead of strtobool()

strtobool() is the same as kstrtobool().
However, the latter is more used within the kernel.

In order to remove strtobool() and slightly simplify kstrtox.h, switch to
the other function name.

While at it, include the corresponding header file (<linux/kstrtox.h>).
Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
Link: https://lore.kernel.org/r/d4432a67b6f769cac0a9ec910ac725298b64e102.1667336095.git.christophe.jaillet@wanadoo.frSigned-off-by: Jakub Kicinski <kuba@kernel.org>

drivers/net/usb/cdc_ncm.c

@@ -43,6 +43,7 @@
 #include <linux/ctype.h>
 #include <linux/etherdevice.h>
 #include <linux/ethtool.h>
+#include <linux/kstrtox.h>
 #include <linux/workqueue.h>
 #include <linux/mii.h>
 #include <linux/crc32.h>
@@ -318,7 +319,7 @@ static ssize_t ndp_to_end_store(struct device *d,  struct device_attribute *attr
 	struct cdc_ncm_ctx *ctx = (struct cdc_ncm_ctx *)dev->data[0];
 	bool enable;
 
-	if (strtobool(buf, &enable))
+	if (kstrtobool(buf, &enable))
 		return -EINVAL;
 
 	/* no change? */

drivers/net/usb/qmi_wwan.c

@@ -13,6 +13,7 @@
 #include <linux/ethtool.h>
 #include <linux/etherdevice.h>
 #include <linux/if_arp.h>
+#include <linux/kstrtox.h>
 #include <linux/mii.h>
 #include <linux/rtnetlink.h>
 #include <linux/usb.h>
@@ -343,7 +344,7 @@ static ssize_t raw_ip_store(struct device *d,  struct device_attribute *attr, co
 	bool enable;
 	int ret;
 
-	if (strtobool(buf, &enable))
+	if (kstrtobool(buf, &enable))
 		return -EINVAL;
 
 	/* no change? */
@@ -492,7 +493,7 @@ static ssize_t pass_through_store(struct device *d,
 	struct qmi_wwan_state *info;
 	bool enable;
 
-	if (strtobool(buf, &enable))
+	if (kstrtobool(buf, &enable))
 		return -EINVAL;
 
 	info = (void *)&dev->data;