iwlwifi: Relax uCode timeout/error checking for 6000g2b

Disable plcp error checking for 6000g2b devices, with wifi/bt coex;
this got trigger too often, disable for now until finding better
trigger point.

Also extend the firmware reload timer much longer for BT coex to make sure
there are will be no mistake to reload firmware too fast and too often.

Signed-off-by: Wey-Yi Guy <wey-yi.w.guy@intel.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>