udf: Fix error paths in udf_new_inode()

I case we failed to allocate memory for inode when creating it, we did not
properly free block already allocated for this inode. Move memory allocation
before the block allocation which fixes this issue (thanks for the idea go to
Ingo Oeser <ioe-lkml@rameria.de>). Also remove a few superfluous
initializations already done in udf_alloc_inode().

Reviewed-by: Ingo Oeser <ioe-lkml@rameria.de>
Signed-off-by: Jan Kara <jack@suse.cz>