m68k: mcf530x: move CPU type to Kconfig and refactor config.mk

This commit intends to stop grepping CPU type in
arch/m68k/cpu/mcf530x/config.mk.

Move the CPU type config options from include/configs/amcore.h
to arch/m68k/Kconfig and refactor the CPU flags select in
arch/m68k/cpu/mcf530x/config.mk.

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Cc: Alison Wang <alison.wang@freescale.com>
Cc: Angelo Dureghello <angelo@sysam.it>
diff --git a/arch/m68k/Kconfig b/arch/m68k/Kconfig
index 0bd780a..8f9b4a7 100644
--- a/arch/m68k/Kconfig
+++ b/arch/m68k/Kconfig
@@ -11,6 +11,9 @@
 config MCF52x2
 	bool
 
+config MCF530x
+	bool
+
 # processor type
 config M5208
 	bool
@@ -40,6 +43,10 @@
 	bool
 	select MCF52x2
 
+config M5307
+	bool
+	select MCF530x
+
 choice
 	prompt "Target select"
 
@@ -114,6 +121,7 @@
 
 config TARGET_AMCORE
 	bool "Support AMCORE"
+	select M5307
 
 endchoice