clk: xgene: Don't build COMMON_CLK_XGENE by default

Building COMMON_CLK_XGENE is pointless, unless we're building for
an XGENE system.
Signed-off-by: Marc Gonzalez <marc.w.gonzalez@free.fr>
Signed-off-by: Stephen Boyd <sboyd@kernel.org>

drivers/clk/Kconfig

@@ -215,7 +215,7 @@ config CLK_QORIQ
 
 config COMMON_CLK_XGENE
 	bool "Clock driver for APM XGene SoC"
-	default y
+	default ARCH_XGENE
 	depends on ARM64 || COMPILE_TEST
 	---help---
 	  Sypport for the APM X-Gene SoC reference, PLL, and device clocks.