refator(mediatek): move pmic.[c|h] to common folder

These two files are identical on MT8192 and MT8195. They can also be
used on MT8188. So move them to common/drivers/pmic/.

Change-Id: I8c12d15f1da79ab5767ac02b3ab70e8508155ee8
diff --git a/plat/mediatek/mt8192/platform.mk b/plat/mediatek/mt8192/platform.mk
index ccc9a71..efc14ec 100644
--- a/plat/mediatek/mt8192/platform.mk
+++ b/plat/mediatek/mt8192/platform.mk
@@ -12,6 +12,7 @@
                  -I${MTK_PLAT}/drivers/gic600/                    \
                  -I${MTK_PLAT}/drivers/gpio/                      \
                  -I${MTK_PLAT}/drivers/lpm/                       \
+                 -I${MTK_PLAT}/drivers/pmic/                      \
                  -I${MTK_PLAT}/drivers/pmic_wrap/                 \
                  -I${MTK_PLAT}/drivers/rtc/                       \
                  -I${MTK_PLAT}/drivers/timer/                     \
@@ -55,6 +56,7 @@
                    ${MTK_PLAT}/drivers/gic600/mt_gic_v3.c                \
                    ${MTK_PLAT}/drivers/gpio/mtgpio_common.c              \
                    ${MTK_PLAT}/drivers/lpm/mt_lp_rm.c                    \
+                   ${MTK_PLAT}/drivers/pmic/pmic.c                       \
                    ${MTK_PLAT}/drivers/pmic_wrap/pmic_wrap_init_v2.c     \
                    ${MTK_PLAT}/drivers/rtc/rtc_common.c                  \
                    ${MTK_PLAT}/drivers/rtc/rtc_mt6359p.c                 \
@@ -63,7 +65,6 @@
                    ${MTK_PLAT_SOC}/aarch64/platform_common.c             \
                    ${MTK_PLAT_SOC}/aarch64/plat_helpers.S                \
                    ${MTK_PLAT_SOC}/bl31_plat_setup.c                     \
-                   ${MTK_PLAT_SOC}/drivers/pmic/pmic.c                   \
                    ${MTK_PLAT_SOC}/plat_pm.c                             \
                    ${MTK_PLAT_SOC}/plat_topology.c                       \
                    ${MTK_PLAT_SOC}/plat_sip_calls.c                      \