iwlwifi: dump "Control and Status Register" when detect uCode HW/SW error

When uCode HW/SW error detected, dumping important CSR (Control and Status
Registers) values.
Also add "csr" debugfs file to dump the current values of CSR defined in
CSR table to syslog.

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