arc: move SYS_MONITOR_BASE setup in Konfig

Following SPARK ARC now has SYS_MONITOR_BASE setup via Kconfig.
This makes "include/configs/*.h" cleaner and more flexible.

Signed-off-by: Alexey Brodkin <abrodkin@synopsys.com>
diff --git a/configs/tb100_defconfig b/configs/tb100_defconfig
index e17a495..b0e8c9f 100644
--- a/configs/tb100_defconfig
+++ b/configs/tb100_defconfig
@@ -2,3 +2,4 @@
 CONFIG_TARGET_TB100=y
 CONFIG_SYS_CLK_FREQ=500000000
 CONFIG_ARC_CACHE_LINE_SHIFT=5
+CONFIG_SYS_TEXT_BASE=0x84000000