iwlwifi: SCD_INT_MSK is obsolete - don't update it

The scheduler can issue an interrupt when moving the read
pointer. To get this interrupt, the driver needs to
configure what queue can issue an interrupt when its read
pointer moves in the scheduler: this is the SCD_INT_MSK.
The driver also needs to enable the interrupt in
CSR_INT_MASK (bit CSR_INT_BIT_SCD).

Since we don't enable the scheduler interrupt in
CSR_INT_MASK, there is no point in requesting an interrupt
from the scheduler: it will be masked anyway. So don't
configure the scheduler to issue interrupts at all.

Signed-off-by: Emmanuel Grumbach <emmanuel.grumbach@intel.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>