feat(mt8186): add Vcore DVFS driver

Add Vcore DVFS to SPM driver.

TEST=build pass
BUG=b:202871018

Change-Id: I52b241b2cdb792be74390cbaa09a728ddbe6593a
diff --git a/plat/mediatek/mt8186/drivers/spm/build.mk b/plat/mediatek/mt8186/drivers/spm/build.mk
index f288691..72a2b6b 100644
--- a/plat/mediatek/mt8186/drivers/spm/build.mk
+++ b/plat/mediatek/mt8186/drivers/spm/build.mk
@@ -20,6 +20,7 @@
 	${CUR_SPM_FOLDER}/mt_spm.c			\
 	${CUR_SPM_FOLDER}/mt_spm_internal.c		\
 	${CUR_SPM_FOLDER}/mt_spm_pmic_wrap.c		\
+	${CUR_SPM_FOLDER}/mt_spm_vcorefs.c		\
 	${CUR_SPM_FOLDER}/mt_spm_conservation.c		\
 	${CUR_SPM_FOLDER}/mt_spm_extern.c