udf: remove redundant assignment of variable etype

Variable etype is being assigned a value that is never read. The
variable and assignment are redundant and can be removed.

Cleans up clang scan build warning:
fs/udf/super.c:2485:10: warning: Although the value stored to 'etype'
is used in the enclosing expression, the value is never actually read
from 'etype' [deadcode.DeadStores]

Link: https://lore.kernel.org/r/20220307152149.139045-1-colin.i.king@gmail.com
Signed-off-by: Colin Ian King <colin.i.king@gmail.com>
Signed-off-by: Jan Kara <jack@suse.cz>