constify more dcache.h inlined helpers.

const struct pointers in commit f0d3b3de ("constify dcache.c
inlined helpers where possible").
This patch allows 'const' in a couple that were added since then.
Signed-off-by: NeilBrown <neilb@suse.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

include/linux/dcache.h

@@ -358,7 +358,7 @@ static inline void dont_mount(struct dentry *dentry)
 
 extern void __d_lookup_done(struct dentry *);
 
-static inline int d_in_lookup(struct dentry *dentry)
+static inline int d_in_lookup(const struct dentry *dentry)
 {
 	return dentry->d_flags & DCACHE_PAR_LOOKUP;
 }
@@ -486,7 +486,7 @@ static inline bool d_really_is_positive(const struct dentry *dentry)
 	return dentry->d_inode != NULL;
 }
 
-static inline int simple_positive(struct dentry *dentry)
+static inline int simple_positive(const struct dentry *dentry)
 {
 	return d_really_is_positive(dentry) && !d_unhashed(dentry);
 }