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/P1020RDB-PD_SPIFLASH_defconfig b/configs/P1020RDB-PD_SPIFLASH_defconfig
index 27625d0..fb6a589 100644
--- a/configs/P1020RDB-PD_SPIFLASH_defconfig
+++ b/configs/P1020RDB-PD_SPIFLASH_defconfig
@@ -20,6 +20,7 @@
 CONFIG_FIT_VERBOSE=y
 CONFIG_OF_BOARD_SETUP=y
 CONFIG_OF_STDOUT_VIA_ALIAS=y
+CONFIG_SPL_SYS_MONITOR_BASE=0xF8F81000
 CONFIG_SPIFLASH=y
 CONFIG_BOOTDELAY=10
 CONFIG_USE_BOOTCOMMAND=y