p9: avoid unused variable warning

Commit 4e34e719 ("fs: take the ACL checks to common code") removed
the use of the 'acl' variable in v9fs_iop_get_acl(), but left the
variable definition around.  Remove it to get rid of the warning:

  fs/9p/acl.c: In function ‘v9fs_iop_get_acl’:
  fs/9p/acl.c:101:20: warning: unused variable ‘acl’
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

fs/9p/acl.c

@@ -98,7 +98,6 @@ static struct posix_acl *v9fs_get_cached_acl(struct inode *inode, int type)
 
 struct posix_acl *v9fs_iop_get_acl(struct inode *inode, int type)
 {
-	struct posix_acl *acl;
 	struct v9fs_session_info *v9ses;
 
 	v9ses = v9fs_inode2v9ses(inode);