cdrom: Remove redundant variable and its assignment

cdrom: Remove redundant variable and its assignment

Variable is not used in functions, and its assignment is redundant too.
So it should be deleted. Also the inner-most set of parentheses is no
longer needed.

The clang_analyzer complains as follows:

drivers/cdrom/cdrom.c:877: warning:

Although the value stored to 'ret' is used in the enclosing expression,
the value is never actually read from 'ret'.

Reported-by: Zeal Robot <zealci@zte.com.cn>
Signed-off-by: luo penghao <luo.penghao@zte.com.cn>
Link: https://lore.kernel.org/all/20211020024229.1036219-1-luo.penghao@zte.com.cn
Signed-off-by: Phillip Potter <phil@philpotter.co.uk>
Link: https://lore.kernel.org/r/20211021074621.901-1-phil@philpotter.co.uk
Signed-off-by: Jens Axboe <axboe@kernel.dk>