soc: mediatek: add vdec item for scpsys

for some chips, there is vdec item in scpsys, this patch adds it.

Signed-off-by: Mars Cheng <[e-mail]>
Signed-off-by: Matthias Brugger <[e-mail]>

drivers/soc/mediatek/mtk-scpsys.c

···
 	CLK_VENC,
 	CLK_VENC_LT,
 	CLK_ETHIF,
+	CLK_VDEC,
 	CLK_MAX,
 };
 
···
 	"venc",
 	"venc_lt",
 	"ethif",
+	"vdec",
 	NULL,
 };