fixup "wifi_drv: fix timer scheduling"
wifi_drv: enable support for iwl7260

- essential support for 7260 chipset and DMA fixes
- assign mvm->pm_ops at beginning of function iwl_op_mode_mvm_start.
  iwl_mvm_mac_setup_register() uses mvm->pm_ops, but it is called
  before this field is set to a valid value.
- disable call to function iwl_mvm_prepare_multicast.
  This function leads to a pagefault, as it aspects a list of multicast
  addresses, but the list is empty as it is not generated by this port.
wifi_drv: adapt wifi.run for iwl7260

Fixes #1317.