qualcomm/ipq806x: add spi_crop_chunk()

That function requirement was added upstream but not in Chromium, so
add an implementation.

Change-Id: Ie384b315adb205586defa730b843c7c8e96f77fb
Signed-off-by: Patrick Georgi <pgeorgi@chromium.org>
Reviewed-on: http://review.coreboot.org/9776
Tested-by: build bot (Jenkins)
Reviewed-by: Stefan Reinauer <stefan.reinauer@coreboot.org>

src/soc/qualcomm/ipq806x/spi.c

@@ -705,6 +705,11 @@ static int spi_xfer_rx_packet(struct ipq_spi_slave *ds,
 	return config_spi_state(ds, SPI_RESET_STATE);
 }
 
+unsigned int spi_crop_chunk(unsigned int cmd_len, unsigned int buf_len)
+{
+	return min(MAX_PACKET_COUNT, buf_len);
+}
+
 int spi_xfer(struct spi_slave *slave, const void *dout,
 	     unsigned out_bytes, void *din, unsigned in_bytes)
 {