ARC: [plat_arcfpga]->[plat_sim]

* Remove remanants of legacy ARC FPGA platforms (AA4, ML509...)
* Only nsim simulation platform is left, rename platform accordingly
* AA4 DT stuff is compatible with nsim for ARC700 so rename it too

Signed-off-by: Vineet Gupta <vgupta@synopsys.com>
diff --git a/arch/arc/Kconfig b/arch/arc/Kconfig
index 8e8de4c..824065a 100644
--- a/arch/arc/Kconfig
+++ b/arch/arc/Kconfig
@@ -81,7 +81,7 @@
 
 menu "ARC Platform/SoC/Board"
 
-source "arch/arc/plat-arcfpga/Kconfig"
+source "arch/arc/plat-sim/Kconfig"
 source "arch/arc/plat-tb10x/Kconfig"
 #New platform adds here