usb: gadget: storage_common: Make fsg_lun_is_open() a function.

Since function-line macros are to be avoided, this commit replaces
the fsg_lun_is_open() macro with a static inline function.

While at it, this commit also adds “inline” modifier to the
fsg_lun_from_dev() function.

Signed-off-by: Michal Nazarewicz <[e-mail]>
Signed-off-by: Felipe Balbi <[e-mail]>

drivers/usb/gadget/storage_common.c

···
 	struct device	dev;
 };
 
-#define fsg_lun_is_open(curlun)	((curlun)->filp != NULL)
+static inline bool fsg_lun_is_open(struct fsg_lun *curlun)
+{
+	return curlun->filp != NULL;
+}
 
-static struct fsg_lun *fsg_lun_from_dev(struct device *dev)
+static inline struct fsg_lun *fsg_lun_from_dev(struct device *dev)
 {
 	return container_of(dev, struct fsg_lun, dev);
 }