linux: remove Blackfin related code

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>

linux/Config.in

@@ -194,7 +194,7 @@ choice
 
 config BR2_LINUX_KERNEL_UIMAGE
 	bool "uImage"
-	depends on BR2_arc || BR2_arm || BR2_armeb || BR2_bfin || \
+	depends on BR2_arc || BR2_arm || BR2_armeb || \
 		   BR2_powerpc || BR2_powerpc64 || BR2_powerpc64le || \
 		   BR2_sh || BR2_mips || BR2_mipsel || \
 		   BR2_mips64 || BR2_mips64el || BR2_xtensa