nios2: kconfig: remove duplicate DEBUG_STACK_USAGE symbol defintions

DEBUG_STACK_USAGE is already defined in lib/Kconfig.debug
Signed-off-by: Tobias Klauser <tklauser@distanz.ch>
Signed-off-by: Ley Foon Tan <ley.foon.tan@intel.com>

arch/nios2/Kconfig.debug

@@ -3,15 +3,6 @@
 config TRACE_IRQFLAGS_SUPPORT
 	def_bool y
 
-config DEBUG_STACK_USAGE
-	bool "Enable stack utilization instrumentation"
-	depends on DEBUG_KERNEL
-	help
-	  Enables the display of the minimum amount of free stack which each
-	  task has ever had available in the sysrq-T and sysrq-P debug output.
-
-	  This option will slow down process creation somewhat.
-
 config EARLY_PRINTK
 	bool "Activate early kernel debugging"
 	default y