Remove Btrfs compat code for older kernels

Btrfs had compatibility code for kernels back to 2.6.18.  These have
been removed, and will be maintained in a separate backport
git tree from now on.

Signed-off-by: Chris Mason <chris.mason@oracle.com>
diff --git a/fs/btrfs/compat.h b/fs/btrfs/compat.h
index b0ed188..cd6598b 100644
--- a/fs/btrfs/compat.h
+++ b/fs/btrfs/compat.h
@@ -1,9 +1,8 @@
 #ifndef _COMPAT_H_
 #define _COMPAT_H_
 
-#if LINUX_VERSION_CODE <= KERNEL_VERSION(2,6,26)
-#define trylock_page(page) (!TestSetPageLocked(page))
-#endif
+#define btrfs_drop_nlink(inode) drop_nlink(inode)
+#define btrfs_inc_nlink(inode)	inc_nlink(inode)
 
 #if LINUX_VERSION_CODE <= KERNEL_VERSION(2,6,27)
 static inline struct dentry *d_obtain_alias(struct inode *inode)
@@ -22,39 +21,4 @@
 }
 #endif
 
-#if LINUX_VERSION_CODE <= KERNEL_VERSION(2,6,18)
-static inline void btrfs_drop_nlink(struct inode *inode)
-{
-	inode->i_nlink--;
-}
-
-static inline void btrfs_inc_nlink(struct inode *inode)
-{
-	inode->i_nlink++;
-}
-#else
-# define btrfs_drop_nlink(inode) drop_nlink(inode)
-# define btrfs_inc_nlink(inode)	inc_nlink(inode)
-#endif
-
-/*
- * Even if AppArmor isn't enabled, it still has different prototypes.
- * Add more distro/version pairs here to declare which has AppArmor applied.
- */
-#if defined(CONFIG_SUSE_KERNEL)
-# if LINUX_VERSION_CODE >= KERNEL_VERSION(2,6,22)
-# define REMOVE_SUID_PATH 1
-# endif
-#endif
-
-/*
- * catch any other distros that have patched in apparmor.  This isn't
- * 100% reliable because it won't catch people that hand compile their
- * own distro kernels without apparmor compiled in.  But, it is better
- * than nothing.
- */
-#ifdef CONFIG_SECURITY_APPARMOR
-# define REMOVE_SUID_PATH 1
-#endif
-
 #endif /* _COMPAT_H_ */