soc: mediatek: mtk-cmdq: Add specific purpose register definitions for GCE

Add specific purpose register definitions for GCE, so CMDQ users can
use them as a buffer to store data.
Signed-off-by: Jason-JH.Lin <jason-jh.lin@mediatek.com>
Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Link: https://lore.kernel.org/r/20240307013458.23550-2-jason-jh.lin@mediatek.comSigned-off-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>

include/linux/soc/mediatek/mtk-cmdq.h

@@ -14,6 +14,15 @@
 #define CMDQ_ADDR_HIGH(addr)	((u32)(((addr) >> 16) & GENMASK(31, 0)))
 #define CMDQ_ADDR_LOW(addr)	((u16)(addr) | BIT(1))
 
+/*
+ * Every cmdq thread has its own SPRs (Specific Purpose Registers),
+ * so there are 4 * N (threads) SPRs in GCE that shares the same indexes below.
+ */
+#define CMDQ_THR_SPR_IDX0	(0)
+#define CMDQ_THR_SPR_IDX1	(1)
+#define CMDQ_THR_SPR_IDX2	(2)
+#define CMDQ_THR_SPR_IDX3	(3)
+
 struct cmdq_pkt;
 
 struct cmdq_client_reg {