arc: rename "arc700" in "arcv1"

As a preparation to ARCv2 port submission we rename "arc700" folder to
"arcv1" which stands for ARCv1 ISA also known as ARCompact.

This will allow us to add more flavours of binary-compatible ARCv1 CPUs
like ARC600 if needed later on and all required ARCv2 CPUs (which are
binary incompatible with ARCv1) in "arcv2" folder in subsequent commits.

Signed-off-by: Alexey Brodkin <abrodkin@synopsys.com>
Signed-off-by: Igor Guryanov <guryanov@synopsys.com>

arch/arc/Kconfig

@@ -5,7 +5,7 @@ config SYS_ARCH
 	default "arc"
 
 config SYS_CPU
-	default "arc700"
+	default "arcv1"
 
 choice
 	prompt "Target select"