iwlagn: don't disable interrupts after the NIC has been reset

It is superfluous to disable the interrupts after we reset the NIC. The only
entity that could enable the interrupts after the NIC is reset is the driver.
So remove this pointless action.

Signed-off-by: Emmanuel Grumbach <emmanuel.grumbach@intel.com>
Signed-off-by: Wey-Yi Guy <wey-yi.w.guy@intel.com>