board/synopsys: remove selection of CPU from the board

Both ARCangel4 and AXS10x are FPGA-based boards so they may have
different CPUs. For now we have only 1 option (ARC700) and we define
this as default in arch Kconfig.
Signed-off-by: NAlexey Brodkin <abrodkin@synopsys.com>

arch/arc/Kconfig

@@ -4,6 +4,9 @@ menu "ARC architecture"
 config SYS_ARCH
 	default "arc"
 
+config SYS_CPU
+	default "arc700"
+
 choice
 	prompt "Target select"
 

board/synopsys/Kconfig

 if TARGET_ARCANGEL4
 
-config SYS_CPU
-	default "arc700"
-
 config SYS_VENDOR
 	default "synopsys"
 
@@ -13,9 +10,6 @@ endif
 
 if TARGET_ARCANGEL4_BE
 
-config SYS_CPU
-	default "arc700"
-
 config SYS_VENDOR
 	default "synopsys"
 

board/synopsys/axs101/Kconfig

 if TARGET_AXS101
 
-config SYS_CPU
-	default "arc700"
-
 config SYS_BOARD
 	default "axs101"