xfs: remove NULL pointer checks in xfs_mru_cache_insert

xfs: remove NULL pointer checks in xfs_mru_cache_insert

Remove the check for a NULL mru or mru->list in xfs_mru_cache_insert
as this API misused lead to a direct NULL pointer dereference on first
use and is not user triggerable.  As a smatch run by Dan points out
with the recent cleanup it would otherwise try to free the object we
just determined to be NULL for this impossible to reach case.

Fixes: 70b95cb86513 ("xfs: free the item in xfs_mru_cache_insert on failure")
Reported-by: Dan Carpenter <dan.carpenter@linaro.org>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Hans Holmberg <hans.holmberg@wdc.com>
Signed-off-by: Carlos Maiolino <cem@kernel.org>