smb: client: Clear sensitive stack and heap data in smb2ops.c

Make sure to not leak key-related data via the heap or the stack
by using kfree_sensitive() or memzero_explicit() here.

Signed-off-by: Thomas Huth <thuth@redhat.com>
Signed-off-by: Namjae Jeon <linkinjeon@kernel.org>
Signed-off-by: Paulo Alcantara <pc@manguebit.org>