block: floppy: Fix uninitialized use of outparam

block: floppy: Fix uninitialized use of outparam

Fix Smatch-detected error:
drivers/block/floppy.c:3569 fd_locked_ioctl() error:
uninitialized symbol 'outparam'.

Smatch may incorrectly warn about uninitialized use of 'outparam'
in fd_locked_ioctl(), even though all _IOC_READ commands guarantee
its initialization. Initialize outparam to NULL to make this explicit
and suppress the false positive.

Signed-off-by: Purva Yeshi <purvayeshi550@gmail.com>
Reviewed-by: Denis Efremov <efremov@linux.com>
Link: https://lore.kernel.org/r/20250713070020.14530-1-purvayeshi550@gmail.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>