remoteproc: qcom: q6v5: Fix NULL vs IS_ERR() bug in q6v5_alloc_memory_region()

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

Fixes: c70b9d5 ("remoteproc: qcom: Use of_reserved_mem_region_* functions for "memory-region"")
Signed-off-by: Dan Carpenter <dan.carpenter@linaro.org>
Link: https://lore.kernel.org/r/674b32a78563282adeaf3cdf941314a0b8181026.1764427595.git.dan.carpenter@linaro.org
Signed-off-by: Bjorn Andersson <andersson@kernel.org>

Author: Dan Carpenter

drivers/remoteproc/qcom_q6v5_wcss.c

@@ -887,9 +887,9 @@ static int q6v5_alloc_memory_region(struct q6v5_wcss *wcss)
 	wcss->mem_reloc = res.start;
 	wcss->mem_size = resource_size(&res);
 	wcss->mem_region = devm_ioremap_resource_wc(dev, &res);
-	if (!wcss->mem_region) {
+	if (IS_ERR(wcss->mem_region)) {
 		dev_err(dev, "unable to map memory region: %pR\n", &res);
-		return -EBUSY;
+		return PTR_ERR(wcss->mem_region);
 	}
 
 	return 0;