Convert CONFIG_SYS_MONITOR_BASE to Kconfig

This converts the following to Kconfig:
   CONFIG_SYS_MONITOR_BASE

Note that for how this is re-used on some PowePC platforms, we introduce
CONFIG_SPL_SYS_MONITOR_BASE and CONFIG_TPL_SYS_MONITOR_BASE and use the
CONFIG_VAL macro to get the correct value at build time, in the code.

Signed-off-by: Tom Rini <trini@konsulko.com>
diff --git a/configs/coreboot_defconfig b/configs/coreboot_defconfig
index 5a0bf1f..b09f3f0 100644
--- a/configs/coreboot_defconfig
+++ b/configs/coreboot_defconfig
@@ -8,6 +8,7 @@
 CONFIG_TARGET_COREBOOT=y
 CONFIG_FIT=y
 CONFIG_FIT_SIGNATURE=y
+CONFIG_SYS_MONITOR_BASE=0x01110000
 CONFIG_SHOW_BOOT_PROGRESS=y
 CONFIG_USE_BOOTARGS=y
 CONFIG_BOOTARGS="root=/dev/sdb3 init=/sbin/init rootwait ro"