UDF: Fix compiler warning

Fix compiler warning

fs/udf/balloc.c: In function 'udf_bitmap_new_block':
fs/udf/balloc.c:273: warning: passing argument 1 of '_find_next_bit_le' from incompatible pointer type
fs/udf/balloc.c:285: warning: passing argument 1 of '_find_next_bit_le' from incompatible pointer type
fs/udf/balloc.c:311: warning: passing argument 1 of '_find_next_bit_le' from incompatible pointer type
fs/udf/balloc.c:325: warning: passing argument 1 of '_find_next_bit_le' from incompatible pointer type

The main fix is to add a cast in ext2_find_next_bit().

As all other usage locations of udf_find_next_one_bit()
directly use bh->b_data (which is a char *), the useless
(char *) cast in line 311 can be removed, too.

Signed-off-by: Dirk Behme <dirk.behme@de.bosch.com>
Signed-off-by: George G. Davis <gdavis@mvista.com>
Signed-off-by: Jan Kara <jack@suse.cz>