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/axs101_defconfig b/configs/axs101_defconfig
index d165e41..34ed963 100644
--- a/configs/axs101_defconfig
+++ b/configs/axs101_defconfig
@@ -2,4 +2,5 @@
 CONFIG_TARGET_AXS101=y
 CONFIG_SYS_CLK_FREQ=750000000
 CONFIG_ARC_CACHE_LINE_SHIFT=5
-CONFIG_SYS_DCACHE_OFF=y
\ No newline at end of file
+CONFIG_SYS_DCACHE_OFF=y
+CONFIG_SYS_TEXT_BASE=0x81000000
\ No newline at end of file