iwlwifi: pcie: wait longer after device reset

The newest devices need a longer time to reset because of
their more complex hardware. Wait 5ms after device reset.
Consolidate all the places that reset the device in the
PCIe transport to avoid future bugs.

While at it, unify the flow to use set_bit instead of full
write as requested by the hardware designers.

Signed-off-by: Emmanuel Grumbach <emmanuel.grumbach@intel.com>
Signed-off-by: Luca Coelho <luciano.coelho@intel.com>