fs: udf: Optimize udf_free_in_core_inode and udf_find_fileset function

These two functions perform the following optimizations.
1. Delete the type cast of foo pointer. Void * does not need to convert
the type.
2. Delete the initialization assignment of bh variable, which is
assigned first.

Signed-off-by: Li zeming <zeming@nfschina.com>
Signed-off-by: Jan Kara <jack@suse.cz>
Link: https://lore.kernel.org/r/20221012104235.3331-1-zeming@nfschina.com