udf: convert UDF_SB_ALLOC_PARTMAPS macro to udf_sb_alloc_partition_maps function

- convert UDF_SB_ALLOC_PARTMAPS macro to udf_sb_alloc_partition_maps function
- convert kmalloc + memset to kcalloc
- check if kcalloc failed (partially)

Signed-off-by: Marcin Slusarz <marcin.slusarz@gmail.com>
Cc: Ben Fennema <bfennema@falcon.csc.calpoly.edu>
Cc: Jan Kara <jack@suse.cz>
Acked-by: Christoph Hellwig <hch@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>