rfkill: document rfkill module parameters

Document the rfkill module parameters default_state and
master_switch_mode.
Signed-off-by: Andrew Clausen <andrew.p.clausen@gmail.com>
[rewrite commit message]
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

Documentation/kernel-parameters.txt

@@ -3180,6 +3180,18 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
 
 	retain_initrd	[RAM] Keep initrd memory after extraction
 
+	rfkill.default_state=
+		0	"airplane mode".  All wifi, bluetooth, wimax, gps, fm,
+			etc. communication is blocked by default.
+		1	Unblocked.
+
+	rfkill.master_switch_mode=
+		0	The "airplane mode" button does nothing.
+		1	The "airplane mode" button toggles between everything
+			blocked and the previous configuration.
+		2	The "airplane mode" button toggles between everything
+			blocked and everything unblocked.
+
 	rhash_entries=	[KNL,NET]
 			Set number of hash buckets for route cache
 

Documentation/rfkill.txt

@@ -25,6 +25,9 @@ whether they can be changed or not:
  - soft block: writable radio block (need not be readable) that is set by
                the system software.
 
+The rfkill subsystem has two parameters, rfkill.default_state and
+rfkill.master_switch_mode, which are documented in kernel-parameters.txt.
+
 
 2. Implementation details