spi: spi-mem: allow specifying a command's extension

In xSPI mode, flashes expect 2-byte opcodes. The second byte is called
the "command extension". There can be 3 types of extensions in xSPI:
repeat, invert, and hex. When the extension type is "repeat", the same
opcode is sent twice. When it is "invert", the second byte is the
inverse of the opcode. When it is "hex" an additional opcode byte based
is sent with the command whose value can be anything.

So, make opcode a 16-bit value and add a 'nbytes', similar to how
multiple address widths are handled.

All usages of sizeof(op->cmd.opcode) also need to be changed to be
op->cmd.nbytes because that is the actual indicator of opcode size.

Signed-off-by: Pratyush Yadav <p.yadav@ti.com>
Reviewed-by: Jagan Teki <jagan@amarulasolutions.com>
diff --git a/drivers/spi/spi-mem.c b/drivers/spi/spi-mem.c
index 427f7c1..541cd0e 100644
--- a/drivers/spi/spi-mem.c
+++ b/drivers/spi/spi-mem.c
@@ -167,6 +167,9 @@
 	if (op->cmd.dtr || op->addr.dtr || op->dummy.dtr || op->data.dtr)
 		return false;
 
+	if (op->cmd.nbytes != 1)
+		return false;
+
 	return true;
 }
 EXPORT_SYMBOL_GPL(spi_mem_default_supports_op);
@@ -273,8 +276,7 @@
 	}
 
 #ifndef __UBOOT__
-	tmpbufsize = sizeof(op->cmd.opcode) + op->addr.nbytes +
-		     op->dummy.nbytes;
+	tmpbufsize = op->cmd.nbytes + op->addr.nbytes + op->dummy.nbytes;
 
 	/*
 	 * Allocate a buffer to transmit the CMD, ADDR cycles with kmalloc() so
@@ -289,7 +291,7 @@
 
 	tmpbuf[0] = op->cmd.opcode;
 	xfers[xferpos].tx_buf = tmpbuf;
-	xfers[xferpos].len = sizeof(op->cmd.opcode);
+	xfers[xferpos].len = op->cmd.nbytes;
 	xfers[xferpos].tx_nbits = op->cmd.buswidth;
 	spi_message_add_tail(&xfers[xferpos], &msg);
 	xferpos++;
@@ -353,7 +355,7 @@
 			tx_buf = op->data.buf.out;
 	}
 
-	op_len = sizeof(op->cmd.opcode) + op->addr.nbytes + op->dummy.nbytes;
+	op_len = op->cmd.nbytes + op->addr.nbytes + op->dummy.nbytes;
 
 	/*
 	 * Avoid using malloc() here so that we can use this code in SPL where
@@ -442,8 +444,7 @@
 	if (!ops->mem_ops || !ops->mem_ops->exec_op) {
 		unsigned int len;
 
-		len = sizeof(op->cmd.opcode) + op->addr.nbytes +
-			op->dummy.nbytes;
+		len = op->cmd.nbytes + op->addr.nbytes + op->dummy.nbytes;
 		if (slave->max_write_size && len > slave->max_write_size)
 			return -EINVAL;