udf: super.c Fix warning: variable 'sbi' set but not used

This fixes this warning when building the kernel:
  CC      fs/udf/super.o
fs/udf/super.c: In function 'udf_load_sequence':
fs/udf/super.c:1582:22: warning: variable 'sbi' set but not used
Please have a look, when you have time and let me know.

Signed-off-by: Justin P. Mattock <justinmattock@gmail.com>
Signed-off-by: Jan Kara <jack@suse.cz>