befs: replace kmalloc/memset 0 by kzalloc

Use kzalloc for clean fs_info allocation like other filesystems.

Signed-off-by: Fabian Frederick <fabf@skynet.be>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>