media: cec: move the core to a separate directory

In preparation for moving CEC drivers to the CEC directory,
move the core to a separate place.
Acked-by: NHans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: NMauro Carvalho Chehab <mchehab+huawei@kernel.org>

drivers/media/cec/Makefile

 # SPDX-License-Identifier: GPL-2.0
-cec-objs := cec-core.o cec-adap.o cec-api.o
-
-ifeq ($(CONFIG_CEC_NOTIFIER),y)
-  cec-objs += cec-notifier.o
-endif
-
-ifeq ($(CONFIG_CEC_PIN),y)
-  cec-objs += cec-pin.o
-endif
-
-ifeq ($(CONFIG_CEC_PIN_ERROR_INJ),y)
-  cec-objs += cec-pin-error-inj.o
-endif
-
-obj-$(CONFIG_CEC_CORE) += cec.o
+obj-y += core/

drivers/media/cec/core/Makefile

+# SPDX-License-Identifier: GPL-2.0
+cec-objs := cec-core.o cec-adap.o cec-api.o
+
+ifeq ($(CONFIG_CEC_NOTIFIER),y)
+  cec-objs += cec-notifier.o
+endif
+
+ifeq ($(CONFIG_CEC_PIN),y)
+  cec-objs += cec-pin.o
+endif
+
+ifeq ($(CONFIG_CEC_PIN_ERROR_INJ),y)
+  cec-objs += cec-pin-error-inj.o
+endif
+
+obj-$(CONFIG_CEC_CORE) += cec.o