clk: lpc18xx: add NXP specific COMMON_CLK_NXP configuration symbol

The change adds COMMON_CLK_NXP configuration symbol and enables it for
NXP LPC18XX architecture, this is needed to reuse drivers/clk/nxp
folder for NXP common clock framework drivers other than LPC18XX one.

Signed-off-by: Vladimir Zapolskiy <vz@mleia.com>
Acked-by: Joachim Eastwood <manabian@gmail.com>
Signed-off-by: Michael Turquette <mturquette@baylibre.com>
diff --git a/drivers/clk/Makefile b/drivers/clk/Makefile
index 820714c..15603c1 100644
--- a/drivers/clk/Makefile
+++ b/drivers/clk/Makefile
@@ -62,8 +62,8 @@
 obj-$(CONFIG_PLAT_ORION)		+= mvebu/
 obj-$(CONFIG_ARCH_MESON)		+= meson/
 obj-$(CONFIG_ARCH_MXS)			+= mxs/
-obj-$(CONFIG_ARCH_LPC18XX)		+= nxp/
 obj-$(CONFIG_MACH_PISTACHIO)		+= pistachio/
+obj-$(CONFIG_COMMON_CLK_NXP)		+= nxp/
 obj-$(CONFIG_COMMON_CLK_PXA)		+= pxa/
 obj-$(CONFIG_COMMON_CLK_QCOM)		+= qcom/
 obj-$(CONFIG_ARCH_ROCKCHIP)		+= rockchip/