[GFS2] Make headers compile on their own

As per Jan Engelhardt's comments, this should make all the headers
compile on their own by including and/or declaring structures
early.

Cc: Jan Engelhardt <jengelh@linux01.gwdg.de>
Signed-off-by: Steven Whitehouse <swhiteho@redhat.com>
diff --git a/fs/gfs2/eattr.h b/fs/gfs2/eattr.h
index 85c70c3..cb7c2d8 100644
--- a/fs/gfs2/eattr.h
+++ b/fs/gfs2/eattr.h
@@ -10,6 +10,9 @@
 #ifndef __EATTR_DOT_H__
 #define __EATTR_DOT_H__
 
+struct gfs2_inode;
+struct iattr;
+
 #define GFS2_EA_REC_LEN(ea) be32_to_cpu((ea)->ea_rec_len)
 #define GFS2_EA_DATA_LEN(ea) be32_to_cpu((ea)->ea_data_len)