firmware: google: fix a NULL vs IS_ERR() check in cbmem_entry_probe()

The devm_memremap() function returns error pointers on error,
it doesn't return NULL.

Fixes: 19d54020 ("firmware: google: Implement cbmem in sysfs driver")
Signed-off-by: NPeng Wu <wupeng58@huawei.com>
Reviewed-by: NGuenter Roeck <groeck@chromium.org>
Reviewed-by: NJack Rosenthal <jrosenth@chromium.org>
Link: https://lore.kernel.org/r/20221115091138.51614-1-wupeng58@huawei.comSigned-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/firmware/google/cbmem.c

@@ -106,8 +106,8 @@ static int cbmem_entry_probe(struct coreboot_device *dev)
 	entry->mem_file_buf = devm_memremap(&dev->dev, dev->cbmem_entry.address,
 					    dev->cbmem_entry.entry_size,
 					    MEMREMAP_WB);
-	if (!entry->mem_file_buf)
-		return -ENOMEM;
+	if (IS_ERR(entry->mem_file_buf))
+		return PTR_ERR(entry->mem_file_buf);
 
 	entry->size = dev->cbmem_entry.entry_size;