hfsplus: fix HFSPLUS_SB calling convention

HFSPLUS_SB doesn't return a pointer to the hfsplus-specific superblock
information like all other FOO_SB macros, but dereference the pointer in a way
that made it look like a direct struct derefence.  This only works as long
as the HFSPLUS_SB macro is used directly and prevents us from keepig a local
hfsplus_sb_info pointer.  Fix the calling convention and introduce a local
sbi variable in all functions that use it constantly.

Signed-off-by: Christoph Hellwig <hch@tuxera.com>
diff --git a/fs/hfsplus/options.c b/fs/hfsplus/options.c
index 572628b..f2598ae 100644
--- a/fs/hfsplus/options.c
+++ b/fs/hfsplus/options.c
@@ -171,7 +171,7 @@
 
 int hfsplus_show_options(struct seq_file *seq, struct vfsmount *mnt)
 {
-	struct hfsplus_sb_info *sbi = &HFSPLUS_SB(mnt->mnt_sb);
+	struct hfsplus_sb_info *sbi = HFSPLUS_SB(mnt->mnt_sb);
 
 	if (sbi->creator != HFSPLUS_DEF_CR_TYPE)
 		seq_printf(seq, ",creator=%.4s", (char *)&sbi->creator);