mm/dmapool: use DEVICE_ATTR_RO macro

Use DEVICE_ATTR_RO() helper instead of plain DEVICE_ATTR(), which makes
the code a bit shorter and easier to read.

Link: https://lkml.kernel.org/r/20210524112852.34716-1-yuehaibing@huawei.com
Signed-off-by: YueHaibing <yuehaibing@huawei.com>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm/dmapool.c

@@ -62,8 +62,7 @@ struct dma_page {		/* cacheable header for 'allocation' bytes */
 static DEFINE_MUTEX(pools_lock);
 static DEFINE_MUTEX(pools_reg_lock);
 
-static ssize_t
-show_pools(struct device *dev, struct device_attribute *attr, char *buf)
+static ssize_t pools_show(struct device *dev, struct device_attribute *attr, char *buf)
 {
 	unsigned temp;
 	unsigned size;
@@ -103,7 +102,7 @@ show_pools(struct device *dev, struct device_attribute *attr, char *buf)
 	return PAGE_SIZE - size;
 }
 
-static DEVICE_ATTR(pools, 0444, show_pools, NULL);
+static DEVICE_ATTR_RO(pools);
 
 /**
  * dma_pool_create - Creates a pool of consistent memory blocks, for dma.