rcu: remove duplicate CONFIG_RCU_CPU_STALL_DETECTOR

Impact: remove the old CONFIG_RCU_CPU_STALL_DETECTOR

tree_rcu introduce CONFIG_RCU_CPU_STALL_DETECTOR again.

These two are the same exactly except:

 the old one "depends on CLASSIC_RCU"
 the new one "depends on CLASSIC_RCU || TREE_RCU"

This patch remove the old one.
Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

lib/Kconfig.debug

@@ -631,19 +631,6 @@ config RCU_TORTURE_TEST_RUNNABLE
 	  Say N here if you want the RCU torture tests to start only
 	  after being manually enabled via /proc.
 
-config RCU_CPU_STALL_DETECTOR
-	bool "Check for stalled CPUs delaying RCU grace periods"
-	depends on CLASSIC_RCU
-	default n
-	help
-	  This option causes RCU to printk information on which
-	  CPUs are delaying the current grace period, but only when
-	  the grace period extends for excessive time periods.
-
-	  Say Y if you want RCU to perform such checks.
-
-	  Say N if you are unsure.
-
 config RCU_CPU_STALL_DETECTOR
 	bool "Check for stalled CPUs delaying RCU grace periods"
 	depends on CLASSIC_RCU || TREE_RCU