udf: fix an uninitialized read bug and remove dead code

In udf_lookup(), the pointer 'fi' is a local variable initialized by the
return value of the function call udf_find_entry(). However, if the macro
'UDF_RECOVERY' is defined, this variable will become uninitialized if the
else branch is not taken, which can potentially cause incorrect results in
the following execution.

To fix this issue, this patch drops the whole code in the ifdef
'UDF_RECOVERY' region, as it is dead code.

Signed-off-by: Wenwen Wang <wang6495@umn.edu>
Signed-off-by: Jan Kara <jack@suse.cz>