btrfs: remove unused le_test_bit()

With commit b18253ec57c0 ("btrfs: optimize free space tree bitmap
conversion"), there are no more callers to le_test_bit(). This patch
removes le_test_bit().

Signed-off-by: Howard McLauchlan <hmclauchlan@fb.com>
Signed-off-by: David Sterba <dsterba@suse.com>

fs/btrfs/extent_io.h

@@ -79,11 +79,6 @@
 #define BITMAP_LAST_BYTE_MASK(nbits) \
 	(BYTE_MASK >> (-(nbits) & (BITS_PER_BYTE - 1)))
 
-static inline int le_test_bit(int nr, const u8 *addr)
-{
-	return 1U & (addr[BIT_BYTE(nr)] >> (nr & (BITS_PER_BYTE-1)));
-}
-
 struct extent_state;
 struct btrfs_root;
 struct btrfs_inode;