i2c: add i2c quirk flag for unsupported clock stretching

Add I2C_AQ_NO_CLK_STRETCH quirk flag, to be used when clock stretching is
not supported.
Signed-off-by: Nicola Corna <nicola@corna.info>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>

include/linux/i2c.h

@@ -493,6 +493,8 @@ struct i2c_adapter_quirks {
 /* convenience macro for typical write-then read case */
 #define I2C_AQ_COMB_WRITE_THEN_READ	(I2C_AQ_COMB | I2C_AQ_COMB_WRITE_FIRST | \
 					 I2C_AQ_COMB_READ_SECOND | I2C_AQ_COMB_SAME_ADDR)
+/* clock stretching is not supported */
+#define I2C_AQ_NO_CLK_STRETCH		BIT(4)
 
 /*
  * i2c_adapter is the structure used to identify a physical i2c bus along