aiodev: imx_thermal: fix breakage after device tree sync

fsl,tempmon-data is a deprecated property that has been replaced
upstream by a NVMEM cell pointing at the calibration value and so
made it into barebox breaking the driver.

Switch to using the new property to fix the regression.

We do not keep support for the old binding around as it would be dead code:
barebox, unlike Linux, is always bundled with a device tree originating
from its build tree and so we only need to ensure the driver matches that
version.

Fixes: abef603 ("dts: update to v5.8-rc1")
Signed-off-by: Ahmad Fatoum <a.fatoum@pengutronix.de>
Reviewed-by: Marco Felsch <m.felsch@pengutronix.de>
Link: https://lore.barebox.org/20230911124808.2748160-1-a.fatoum@pengutronix.de
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>

drivers/aiodev/imx_thermal.c

@@ -22,14 +22,14 @@
 #include <linux/math64.h>
 #include <linux/log2.h>
 #include <linux/clk.h>
+#include <linux/nvmem-consumer.h>
 #include <mach/imx/imx6-anadig.h>
 #include <io.h>
 #include <aiodev.h>
 #include <mfd/syscon.h>
 
 #define FACTOR0			10000000
 #define MEASURE_FREQ		327
-#define OCOTP_ANA1_OFFSET      (0xE * sizeof(uint32_t))
 
 struct imx_thermal_data {
 	int c1, c2;
@@ -109,30 +109,13 @@ static int imx_thermal_read(struct aiochannel *chan, int *val)
 static int imx_thermal_probe(struct device *dev)
 {
 	uint32_t ocotp_ana1;
-	struct device_node *node;
 	struct imx_thermal_data *imx_thermal;
-	struct cdev *ocotp;
 	int t1, n1, t2, n2;
 	int ret;
 
-	node = of_parse_phandle(dev->of_node, "fsl,tempmon-data", 0);
-	if (!node) {
-		dev_err(dev, "No calibration data source\n");
-		return -ENODEV;
-	}
-
-	ocotp = cdev_by_device_node(node);
-	if (!ocotp) {
-		dev_err(dev, "No OCOTP character device\n");
-		return -ENODEV;
-	}
-
-	ret = cdev_read(ocotp, &ocotp_ana1, sizeof(ocotp_ana1),
-			OCOTP_ANA1_OFFSET, 0);
-	if (ret != sizeof(ocotp_ana1)) {
-		dev_err(dev, "Failed to read calibration data\n");
-		return ret < 0 ? ret : -EIO;
-	}
+	ret = nvmem_cell_read_variable_le_u32(dev, "calib", &ocotp_ana1);
+	if (ret)
+		return ret;
 
 	imx_thermal = xzalloc(sizeof(*imx_thermal));
 	imx_thermal->base = syscon_base_lookup_by_phandle(dev->of_node,