fs/cifs/sess.c: Remove set but not used variable 'capabilities'

Fixes gcc '-Wunused-but-set-variable' warning:

fs/cifs/sess.c: In function sess_auth_lanman:
fs/cifs/sess.c:910:8: warning: variable capabilities set but not used [-Wunused-but-set-variable]

Reported-by: Hulk Robot <hulkci@huawei.com>
Signed-off-by: zhengbin <zhengbin13@huawei.com>
Signed-off-by: Steve French <stfrench@microsoft.com>