mei: vsc: Enhance SPI transfer of IVSC ROM

Before downloading firmware, a command response is required to
identify the silicon. However, when downloading IVSC firmware,
reading data from the SPI transfers with the IVSC ROM is not
necessary. Therefore, the rx buffer of SPI transfer command is
determined based on the specific request of the caller.

Fixes: 566f5ca9 ("mei: Add transport driver for IVSC device")
Signed-off-by: Wentong Wu <wentong.wu@intel.com>
Tested-by: Jason Chen <jason.z.chen@intel.com>
Acked-by: Tomas Winker <tomas.winker@intel.com>
Acked-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Link: https://lore.kernel.org/r/20240625081047.4178494-5-wentong.wu@intel.comSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/misc/mei/vsc-tp.c

@@ -331,7 +331,7 @@ int vsc_tp_rom_xfer(struct vsc_tp *tp, const void *obuf, void *ibuf, size_t len)
 		return ret;
 	}
 
-	ret = vsc_tp_dev_xfer(tp, tp->tx_buf, tp->rx_buf, len);
+	ret = vsc_tp_dev_xfer(tp, tp->tx_buf, ibuf ? tp->rx_buf : NULL, len);
 	if (ret)
 		return ret;