Convert CONFIG_ARCH_CPU_INIT to Kconfig

This converts the following to Kconfig:
   CONFIG_ARCH_CPU_INIT

Signed-off-by: Adam Ford <aford173@gmail.com>
Acked-by: Chris Packham <chris.packham@alliedtelesis.co.nz>
Tested-by: Felix Brack <fb@ltec.ch>
diff --git a/configs/ib62x0_defconfig b/configs/ib62x0_defconfig
index 4998db3..13a2e83 100644
--- a/configs/ib62x0_defconfig
+++ b/configs/ib62x0_defconfig
@@ -1,5 +1,6 @@
 CONFIG_ARM=y
 CONFIG_SYS_DCACHE_OFF=y
+CONFIG_ARCH_CPU_INIT=y
 CONFIG_KIRKWOOD=y
 CONFIG_SYS_TEXT_BASE=0x600000
 CONFIG_TARGET_IB62X0=y