spi: cadence-qspi: Make sure we filter out unsupported ops

The Cadence driver does not support anything else than repeating the
command opcode twice while in octal DTR mode. Make this clear by
checking for this in the ->supports_op() hook.

Reviewed-by: Pratyush Yadav <pratyush@kernel.org>
Tested-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Signed-off-by: Miquel Raynal (Schneider Electric) <miquel.raynal@bootlin.com>
Tested-by: Santhosh Kumar K <s-k6@ti.com>
Link: https://patch.msgid.link/20260122-schneider-6-19-rc1-qspi-v4-7-f9c21419a3e6@bootlin.com
Signed-off-by: Mark Brown <broonie@kernel.org>

Author: miquelraynal

drivers/spi/spi-cadence-quadspi.c

@@ -1531,6 +1531,10 @@ static bool cqspi_supports_mem_op(struct spi_mem *mem,
 			return false;
 		if (op->data.nbytes && op->data.buswidth != 8)
 			return false;
+
+		/* A single opcode is supported, it will be repeated */
+		if ((op->cmd.opcode >> 8) != (op->cmd.opcode & 0xFF))
+			return false;
 	} else if (!all_false) {
 		/* Mixed DTR modes are not supported. */
 		return false;