NFC: trf7970a: Correct register settings for 27MHz clock

In prior commits the selected clock frequency does not propagate
correctly to what is written to the TRF7970A_MODULATOR_SYS_CLK_CTRL
register.
Signed-off-by: Geoff Lansberry <geoff@kuvee.com>
Acked-by: Mark Greer <mgreer@animalcreek.com>
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>

drivers/nfc/trf7970a.c

@@ -2049,6 +2049,13 @@ static int trf7970a_probe(struct spi_device *spi)
 		return -EINVAL;
 	}
 
+	if (clk_freq == TRF7970A_27MHZ_CLOCK_FREQUENCY) {
+		trf->modulator_sys_clk_ctrl = TRF7970A_MODULATOR_27MHZ;
+		dev_dbg(trf->dev, "trf7970a configured for 27MHz crystal\n");
+	} else {
+		trf->modulator_sys_clk_ctrl = 0;
+	}
+
 	ret = devm_request_threaded_irq(trf->dev, spi->irq, NULL,
 					trf7970a_irq,
 					IRQF_TRIGGER_RISING | IRQF_ONESHOT,