sh: Move build rule for cchips/hd6446x/ to arch/sh/Kbuild

This is the last user of core-y in arch/sh.

Use the standard obj-y syntax.
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Acked-by: Randy Dunlap <rdunlap@infradead.org>
Tested-by: Randy Dunlap <rdunlap@infradead.org>
Reviewed-by: John Paul Adrian Glaubitz <glaubitz@physik.fu-berlin.de>
Link: https://lore.kernel.org/r/20230219141555.2308306-2-masahiroy@kernel.orgSigned-off-by: John Paul Adrian Glaubitz <glaubitz@physik.fu-berlin.de>

arch/sh/Kbuild

@@ -3,5 +3,7 @@ obj-y				+= kernel/ mm/ boards/
 obj-$(CONFIG_SH_FPU_EMU)	+= math-emu/
 obj-$(CONFIG_USE_BUILTIN_DTB)	+= boot/dts/
 
+obj-$(CONFIG_HD6446X_SERIES)	+= cchips/hd6446x/
+
 # for cleaning
 subdir- += boot

arch/sh/Makefile

@@ -126,9 +126,6 @@ machdir-$(CONFIG_SH_X3PROTO)			+= mach-x3proto
 machdir-$(CONFIG_SH_LANDISK)			+= mach-landisk
 machdir-y					+= mach-common
 
-# Companion chips
-core-$(CONFIG_HD6446X_SERIES)	+= arch/sh/cchips/hd6446x/
-
 #
 # CPU header paths
 #