fbdev: Clean up forward declarations in header file

Add forward declarations for struct i2c_adapter and struct module, and
sort the list alphabetically.

Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Reviewed-by: Jani Nikula <jani.nikula@intel.com>
Acked-by: Helge Deller <deller@gmx.de>
Link: https://patchwork.freedesktop.org/patch/msgid/20240219093941.3684-9-tzimmermann@suse.de

include/linux/fb.h

@@ -15,15 +15,17 @@
 #include <asm/fb.h>
 
 struct backlight_device;
-struct vm_area_struct;
-struct fb_info;
 struct device;
+struct device_node;
+struct fb_info;
 struct file;
+struct i2c_adapter;
 struct inode;
+struct module;
 struct notifier_block;
 struct page;
 struct videomode;
-struct device_node;
+struct vm_area_struct;
 
 /* Definitions below are used in the parsed monitor specs */
 #define FB_DPMS_ACTIVE_OFF	1