ext4: pass a char * to ext4_count_free() instead of a buffer_head ptr

Make it possible for ext4_count_free to operate on buffers and not
just data in buffer_heads.

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
Cc: stable@kernel.org

diff --cc fs/ext4/balloc.c
Simple merge

diff --cc fs/ext4/bitmap.c
Simple merge

diff --cc fs/ext4/ext4.h
Simple merge

diff --cc fs/ext4/ialloc.c
Simple merge