mediatek: move uart.h to common folder

UART register definition is the same on MediaTek platforms.
Move uart.h to common folder and remove the duplicate file.

Change-Id: Iea0931dfd606ae4a7ab475b9cb3a08dc6de68b36
diff --git a/plat/mediatek/mt8183/platform.mk b/plat/mediatek/mt8183/platform.mk
index 07da1af..1615cf9 100644
--- a/plat/mediatek/mt8183/platform.mk
+++ b/plat/mediatek/mt8183/platform.mk
@@ -8,6 +8,7 @@
 MTK_PLAT_SOC  := ${MTK_PLAT}/${PLAT}
 
 PLAT_INCLUDES := -I${MTK_PLAT}/common/                            \
+                 -I${MTK_PLAT}/common/drivers/uart/                \
                  -I${MTK_PLAT_SOC}/drivers/                       \
                  -I${MTK_PLAT_SOC}/drivers/emi_mpu/               \
                  -I${MTK_PLAT_SOC}/drivers/devapc/                \
@@ -19,7 +20,6 @@
                  -I${MTK_PLAT_SOC}/drivers/spm/                   \
                  -I${MTK_PLAT_SOC}/drivers/sspm/                  \
                  -I${MTK_PLAT_SOC}/drivers/rtc/                   \
-                 -I${MTK_PLAT_SOC}/drivers/uart/                  \
                  -I${MTK_PLAT_SOC}/include/
 
 PLAT_BL_COMMON_SOURCES := lib/xlat_tables/aarch64/xlat_tables.c       \