9p: Reduce object size with CONFIG_NET_9P_DEBUG

Reduce object size by deduplicating formats.

Use vsprintf extension %pV.
Rename P9_DPRINTK uses to p9_debug, align arguments.
Add function for _p9_debug and macro to add __func__.
Add missing "\n"s to p9_debug uses.
Remove embedded function names as p9_debug adds it.
Remove P9_EPRINTK macro and convert use to pr_<level>.
Add and use pr_fmt and pr_<level>.

$ size fs/9p/built-in.o*
   text	   data	    bss	    dec	    hex	filename
  62133	    984	  16000	  79117	  1350d	fs/9p/built-in.o.new
  67342	    984	  16928	  85254	  14d06	fs/9p/built-in.o.old
$ size net/9p/built-in.o*
   text	   data	    bss	    dec	    hex	filename
  88792	   4148	  22024	 114964	  1c114	net/9p/built-in.o.new
  94072	   4148	  23232	 121452	  1da6c	net/9p/built-in.o.old

Signed-off-by: Joe Perches <joe@perches.com>
Signed-off-by: Eric Van Hensbergen <ericvh@gmail.com>
diff --git a/fs/9p/vfs_dentry.c b/fs/9p/vfs_dentry.c
index e022890..d529437 100644
--- a/fs/9p/vfs_dentry.c
+++ b/fs/9p/vfs_dentry.c
@@ -53,8 +53,8 @@
 
 static int v9fs_dentry_delete(const struct dentry *dentry)
 {
-	P9_DPRINTK(P9_DEBUG_VFS, " dentry: %s (%p)\n", dentry->d_name.name,
-									dentry);
+	p9_debug(P9_DEBUG_VFS, " dentry: %s (%p)\n",
+		 dentry->d_name.name, dentry);
 
 	return 1;
 }
@@ -66,8 +66,8 @@
  */
 static int v9fs_cached_dentry_delete(const struct dentry *dentry)
 {
-	P9_DPRINTK(P9_DEBUG_VFS, " dentry: %s (%p)\n",
-		   dentry->d_name.name, dentry);
+	p9_debug(P9_DEBUG_VFS, " dentry: %s (%p)\n",
+		 dentry->d_name.name, dentry);
 
 	/* Don't cache negative dentries */
 	if (!dentry->d_inode)
@@ -86,8 +86,8 @@
 	struct v9fs_dentry *dent;
 	struct p9_fid *temp, *current_fid;
 
-	P9_DPRINTK(P9_DEBUG_VFS, " dentry: %s (%p)\n", dentry->d_name.name,
-									dentry);
+	p9_debug(P9_DEBUG_VFS, " dentry: %s (%p)\n",
+		 dentry->d_name.name, dentry);
 	dent = dentry->d_fsdata;
 	if (dent) {
 		list_for_each_entry_safe(current_fid, temp, &dent->fidlist,