remoteproc: imx_dsp_rproc: Fix NULL vs IS_ERR() bug in imx_dsp_rproc_add_carveout()

The devm_ioremap_resource_wc() function never returns NULL, it returns
error pointers.  Update the error checking to match.

Fixes: 67a7bc7 ("remoteproc: Use of_reserved_mem_region_* functions for "memory-region"")
Signed-off-by: Dan Carpenter <dan.carpenter@linaro.org>
Reviewed-by: Iuliana Prodan <iuliana.prodan@nxp.com>
Link: https://lore.kernel.org/r/aSf6OerBbPcxBUVt@stanley.mountain
Signed-off-by: Mathieu Poirier <mathieu.poirier@linaro.org>

Author: Dan Carpenter

drivers/remoteproc/imx_dsp_rproc.c

@@ -710,9 +710,9 @@ static int imx_dsp_rproc_add_carveout(struct imx_dsp_rproc *priv)
 			return -EINVAL;
 
 		cpu_addr = devm_ioremap_resource_wc(dev, &res);
-		if (!cpu_addr) {
+		if (IS_ERR(cpu_addr)) {
 			dev_err(dev, "failed to map memory %pR\n", &res);
-			return -ENOMEM;
+			return PTR_ERR(cpu_addr);
 		}
 
 		/* Register memory region */