arch/bfin: internal backend not suitable for some cores

Some cores are not supported by upstream gcc.

Use the newly-introduced symbol to state so, rather than have the
exclusion in the toolchain choice.

Signed-off-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
Cc: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Cc: Arnout Vandecappelle <arnout@mind.be>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>

arch/Config.in.bfin

@@ -6,12 +6,16 @@ choice
 	  Specify target CPU
 config BR2_bf606
 	bool "bf606"
+	select BR2_ARCH_HAS_NO_TOOLCHAIN_BUILDROOT
 config BR2_bf607
 	bool "bf607"
+	select BR2_ARCH_HAS_NO_TOOLCHAIN_BUILDROOT
 config BR2_bf608
 	bool "bf608"
+	select BR2_ARCH_HAS_NO_TOOLCHAIN_BUILDROOT
 config BR2_bf609
 	bool "bf609"
+	select BR2_ARCH_HAS_NO_TOOLCHAIN_BUILDROOT
 config BR2_bf512
 	bool "bf512"
 config BR2_bf514

toolchain/Config.in

@@ -44,10 +44,6 @@ config BR2_TOOLCHAIN_BUILDROOT
 	bool "Buildroot toolchain"
 	select BR2_TOOLCHAIN_HAS_SHADOW_PASSWORDS
 	depends on BR2_ARCH_HAS_TOOLCHAIN_BUILDROOT
-	depends on !BR2_bf606
-	depends on !BR2_bf607
-	depends on !BR2_bf608
-	depends on !BR2_bf609
 
 config BR2_TOOLCHAIN_EXTERNAL
 	bool "External toolchain"