powerpc: Remove unused/obsolete CONFIG_XICS

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
diff --git a/arch/powerpc/platforms/Kconfig b/arch/powerpc/platforms/Kconfig
index 83c704a..f970ca2 100644
--- a/arch/powerpc/platforms/Kconfig
+++ b/arch/powerpc/platforms/Kconfig
@@ -70,11 +70,6 @@
 	depends on PPC_CELLEB
 	default n
 
-config XICS
-	depends on PPC_PSERIES
-	bool
-	default y
-
 config IPIC
 	bool
 	default n