nxp: Make board/freescale/common/Kconfig safe to include once in arch/Kconfig

The way that we use this file currently means that we have to guard it
in every platform Kconfig.  But it is also required in all NXP
platforms, including non-reference platforms.  Make all options in it
have appropriate dependencies so that we can include it a single time
under arch/Kconfig

Signed-off-by: Tom Rini <trini@konsulko.com>
diff --git a/configs/kmcent2_defconfig b/configs/kmcent2_defconfig
index 8540923..37529f2 100644
--- a/configs/kmcent2_defconfig
+++ b/configs/kmcent2_defconfig
@@ -11,6 +11,7 @@
 CONFIG_TARGET_KMCENT2=y
 CONFIG_MPC85XX_HAVE_RESET_VECTOR=y
 CONFIG_ENABLE_36BIT_PHYS=y
+# CONFIG_DEEP_SLEEP is not set
 CONFIG_KM_DEF_NETDEV="eth2"
 CONFIG_KM_IVM_BUS=2
 CONFIG_MP=y