nios2: Build infrastructure

This patch adds Makefile and Kconfig files required for building a
nios2 kernel.

Signed-off-by: Ley Foon Tan <lftan@altera.com>

arch/nios2/Kconfig.debug

@@ -0,0 +1,17 @@
+menu "Kernel hacking"
+
+config TRACE_IRQFLAGS_SUPPORT
+	def_bool y
+
+source "lib/Kconfig.debug"
+
+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.
+
+endmenu