Access to cmd register is racey, especially in smp environments. Protect
it using a spinlock.
Signed-off-by: NMatthieu Bucchianeri <matthieu@vmware.com>
Signed-off-by: NShreyas N Bhatewara <sbhatewara@vmware.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>