Do not build moto config while building MSI

Moto kernel config does not really take effect during
building MSI.
Set to PRODUCT_SPECIFIC_DEFCONFIGS to KERNEL_DEFCONFIG,
So that MSI build can commonize.
It's for build failure
+++
FAILED: ninja:
'kernel/msm-4.19/arch/arm64/configs/vendor/ext_config/moto-kona.config',
needed by
'out/target/product/msi/obj/kernel/msm-4.19/mapphone_defconfig', missing
and no known rule to make it
ninja failed with: exit status 1
+++

Change-Id: I59710763d8a88a89e6e592dcfde53c7e5486d195
Signed-off-by: zhaoxp3 <zhaoxp3@motorola.com>
Reviewed-on: https://gerrit.mot.com/1499582
SLTApproved: Slta Waiver
SME-Granted: SME Approvals Granted
Tested-by: Jira Key
Reviewed-by: Wang Wang <wangwang1@lenovo.com>
Submit-Approved: Jira Key

defconfig.mk

@@ -34,6 +34,10 @@ define do-make-defconfig
 	( perl -le 'print "# This file was automatically generated from:\n#\t" . join("\n#\t", @ARGV) . "\n"' $(2) && cat $(2) ) > $(1) || ( rm -f $(1) && false )
 endef
 
+#When building MSI, moto config does not really take effect
+ifneq ($(findstring msi, $(TARGET_PRODUCT)),)
+PRODUCT_SPECIFIC_DEFCONFIGS := $(DEFCONFIGSRC)/$(KERNEL_DEFCONFIG)
+endif
 #
 # make combined defconfig file
 #---------------------------------------