i2c: xgene: Avoid dma_buffer overrun

SMBus block command uses the first byte of buffer for the data length.
The dma_buffer should be increased by 1 to avoid the overrun issue.
Reported-by: Phil Endecott <phil_gjouf_endecott@chezphil.org>
Signed-off-by: Hoan Tran <hotran@apm.com>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>
Cc: stable@kernel.org

drivers/i2c/busses/i2c-xgene-slimpro.c

@@ -105,7 +105,7 @@ struct slimpro_i2c_dev {
 	struct mbox_chan *mbox_chan;
 	struct mbox_client mbox_client;
 	struct completion rd_complete;
-	u8 dma_buffer[I2C_SMBUS_BLOCK_MAX];
+	u8 dma_buffer[I2C_SMBUS_BLOCK_MAX + 1]; /* dma_buffer[0] is used for length */
 	u32 *resp_msg;
 };