iwlwifi: pcie: config regs according to fw tlv

Sometimes there is a need to configure some registers for
setting some FW properties, such as the FW monitor mode
(internal/external). This patch supports setting this for
PCIe mode.

Signed-off-by: Liad Kaufman <liad.kaufman@intel.com>
Reviewed-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Emmanuel Grumbach <emmanuel.grumbach@intel.com>