microblaze: Fix missing NR_CPUS in menuconfig

The time Kconfig expects that NR_CPUS is defined.

This patch remove this config warning:
"kernel/time/Kconfig:163:warning: range is invalid"

Signed-off-by: Michal Simek <michal.simek@xilinx.com>
diff --git a/arch/microblaze/Kconfig b/arch/microblaze/Kconfig
index 6feded3..a7736fa 100644
--- a/arch/microblaze/Kconfig
+++ b/arch/microblaze/Kconfig
@@ -129,6 +129,10 @@
 
 menu "Kernel features"
 
+config NR_CPUS
+	int
+	default "1"
+
 config ADVANCED_OPTIONS
 	bool "Prompt for advanced kernel configuration options"
 	help