soc/intel/Makefile.inc: Add comment where CONFIG_CSE_*_FILE are used

commit 06cb756f02 ("soc/intel/common/block/cse/Kconfig: Remove
unused symbols") removed these Kconfigs since it's not obvious where
they're used. Add a comment to make it easier to grep for their uses.

Change-Id: I27d94e8a558d6e73004d45cd2aedd94678d29b94
Signed-off-by: Reka Norman <rekanorman@chromium.org>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/78041
Reviewed-by: Yu-Ping Wu <yupingso@google.com>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

src/soc/intel/Makefile.inc

@@ -33,6 +33,18 @@ $(call cse_add_decomp,bp1,$(1))
 $(call cse_add_decomp,bp2,$(1))
 endef
 
+# (Comment to help with greping for uses)
+#
+# This uses the following Kconfigs:
+# CSE_PMCP_FILE
+# CSE_IOMP_FILE
+# CSE_TBTP_FILE
+# CSE_NPHY_FILE
+# CSE_PCHC_FILE
+# CSE_IUNP_FILE
+# CSE_OEMP_FILE
+#
+# For example `$(call cse_add_input_to_bp1_bp2,PMCP)` will process CONFIG_CSE_PMCP_FILE
 define cse_add_input
 $(call cse_add_file,cse_input_files,$(call cse_input_path,$(CONFIG_CSE_$(2)_FILE)),$(1),$(2))
 endef