crypto: inside-secure - do not overwrite the threshold value

This patch fixes the Inside Secure SafeXcel driver not to overwrite the
interrupt threshold value. In certain cases the value of this register,
which controls when to fire an interrupt, was overwritten. This lead to
packet not being processed or acked as the driver never was aware of
their completion.

This patch fixes this behaviour by not setting the threshold when
requests are being processed by the engine.

Fixes: dc7e28a3 ("crypto: inside-secure - dequeue all requests at once")
Suggested-by: Ofer Heifetz <oferh@marvell.com>
Signed-off-by: Antoine Tenart <antoine.tenart@bootlin.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>