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/at91sam9263ek_norflash_defconfig b/configs/at91sam9263ek_norflash_defconfig
index 68c3dcc..fbdf01f 100644
--- a/configs/at91sam9263ek_norflash_defconfig
+++ b/configs/at91sam9263ek_norflash_defconfig
@@ -18,6 +18,7 @@
 CONFIG_DEBUG_UART_CLOCK=100000000
 CONFIG_DEBUG_UART=y
 CONFIG_SYS_LOAD_ADDR=0x22000000
+CONFIG_SYS_MONITOR_BASE=0x10000000
 CONFIG_BOOTDELAY=3
 CONFIG_SYS_CONSOLE_IS_IN_ENV=y
 # CONFIG_DISPLAY_BOARDINFO is not set