iwlwifi: remove references to unsupported HW

There are still some references to 3945 and 4965 HW, which were never
supported in iwlwifi.  These references were inherited from a previous
project and are irrelevant here.  Additionally, remove some irrelevant
references to 5100 HW.  Remove all these.

Signed-off-by: Luca Coelho <luciano.coelho@intel.com>

drivers/net/wireless/intel/iwlwifi/iwl-csr.h

@@ -169,7 +169,7 @@
 
 /*
  * CSR Hardware Revision Workaround Register.  Indicates hardware rev;
- * "step" determines CCK backoff for txpower calculation.  Used for 4965 only.
+ * "step" determines CCK backoff for txpower calculation.
  * See also CSR_HW_REV register.
  * Bit fields:
  *  3-2:  0 = A, 1 = B, 2 = C, 3 = D step