ext4: rename {ext,idx}_pblock and inline small extent functions

Cleanup namespace leaks from fs/ext4 and the inline trivial functions
ext4_{ext,idx}_pblock() and ext4_{ext,idx}_store_pblock() since the
code size actually shrinks when we make these functions inline,
they're so trivial.

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
diff --git a/fs/ext4/migrate.c b/fs/ext4/migrate.c
index 1765c2c..25f3a97 100644
--- a/fs/ext4/migrate.c
+++ b/fs/ext4/migrate.c
@@ -412,7 +412,7 @@
 	struct buffer_head *bh;
 	struct ext4_extent_header *eh;
 
-	block = idx_pblock(ix);
+	block = ext4_idx_pblock(ix);
 	bh = sb_bread(inode->i_sb, block);
 	if (!bh)
 		return -EIO;