Convert CONFIG_SCSI to Kconfig

This converts the following to Kconfig:
   CONFIG_SCSI

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>
diff --git a/arch/powerpc/cpu/mpc86xx/Kconfig b/arch/powerpc/cpu/mpc86xx/Kconfig
index fcac658..2cc180d 100644
--- a/arch/powerpc/cpu/mpc86xx/Kconfig
+++ b/arch/powerpc/cpu/mpc86xx/Kconfig
@@ -21,6 +21,7 @@
 config TARGET_MPC8641HPCN
 	bool "Support MPC8641HPCN"
 	select ARCH_MPC8641
+	imply SCSI
 
 config TARGET_XPEDITE517X
 	bool "Support xpedite517x"