rcutorture: Add documentation for recent conditional and polled APIs

This commit adds kernel-parameters.txt documentation for rcutorture's
(relatively) new gp_cond_exp, gp_cond_full, gp_cond_exp, gp_poll,
gp_poll_exp, gp_poll_full, and gp_poll_exp module parameters.

Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Uladzislau Rezki (Sony) <urezki@gmail.com>

Documentation/admin-guide/kernel-parameters.txt

@@ -5362,7 +5362,23 @@
 
 	rcutorture.gp_cond= [KNL]
 			Use conditional/asynchronous update-side
-			primitives, if available.
+			normal-grace-period primitives, if available.
+
+	rcutorture.gp_cond_exp= [KNL]
+			Use conditional/asynchronous update-side
+			expedited-grace-period primitives, if available.
+
+	rcutorture.gp_cond_full= [KNL]
+			Use conditional/asynchronous update-side
+			normal-grace-period primitives that also take
+			concurrent expedited grace periods into account,
+			if available.
+
+	rcutorture.gp_cond_exp_full= [KNL]
+			Use conditional/asynchronous update-side
+			expedited-grace-period primitives that also take
+			concurrent normal grace periods into account,
+			if available.
 
 	rcutorture.gp_exp= [KNL]
 			Use expedited update-side primitives, if available.
@@ -5371,6 +5387,24 @@
 			Use normal (non-expedited) asynchronous
 			update-side primitives, if available.
 
+	rcutorture.gp_poll= [KNL]
+			Use polled update-side normal-grace-period
+			primitives, if available.
+
+	rcutorture.gp_poll_exp= [KNL]
+			Use polled update-side expedited-grace-period
+			primitives, if available.
+
+	rcutorture.gp_poll_full= [KNL]
+			Use polled update-side normal-grace-period
+			primitives that also take concurrent expedited
+			grace periods into account, if available.
+
+	rcutorture.gp_poll_exp_full= [KNL]
+			Use polled update-side expedited-grace-period
+			primitives that also take concurrent normal
+			grace periods into account, if available.
+
 	rcutorture.gp_sync= [KNL]
 			Use normal (non-expedited) synchronous
 			update-side primitives, if available.  If all