xfs: Fix build breakage in xfs_iops.c when CONFIG_FS_POSIX_ACL is not set

commit 4e34e719, that takes the ACL checks to common code,
accidentely broke the build when CONFIG_FS_POSIX_ACL is not set:

  CC      fs/xfs/linux-2.6/xfs_iops.o
fs/xfs/linux-2.6/xfs_iops.c:1025:14: error: ‘xfs_get_acl’ undeclared here (not in a function)

Fix this by declaring xfs_get_acl a static inline function.
Signed-off-by: NMarkus Trippelsdorf <markus@trippelsdorf.de>
Signed-off-by: NAlex Elder <aelder@sgi.com>

fs/xfs/xfs_acl.h

@@ -51,7 +51,10 @@ extern int posix_acl_default_exists(struct inode *inode);
 extern const struct xattr_handler xfs_xattr_acl_access_handler;
 extern const struct xattr_handler xfs_xattr_acl_default_handler;
 #else
-# define xfs_get_acl(inode, type)			NULL
+static inline struct posix_acl *xfs_get_acl(struct inode *inode, int type)
+{
+	return NULL;
+}
 # define xfs_inherit_acl(inode, default_acl)		0
 # define xfs_acl_chmod(inode)				0
 # define posix_acl_access_exists(inode)			0