memory: tegra30-emc: use DEFINE_SHOW_ATTRIBUTE to simplify code

Use DEFINE_SHOW_ATTRIBUTE helper macro to simplify the code.
No functional change.
Signed-off-by: Liu Shixin <liushixin2@huawei.com>
Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Link: https://lore.kernel.org/r/20220926130025.1061373-3-liushixin2@huawei.com

drivers/memory/tegra/tegra30-emc.c

@@ -1359,20 +1359,7 @@ static int tegra_emc_debug_available_rates_show(struct seq_file *s, void *data)
 
 	return 0;
 }
-
-static int tegra_emc_debug_available_rates_open(struct inode *inode,
-						struct file *file)
-{
-	return single_open(file, tegra_emc_debug_available_rates_show,
-			   inode->i_private);
-}
-
-static const struct file_operations tegra_emc_debug_available_rates_fops = {
-	.open = tegra_emc_debug_available_rates_open,
-	.read = seq_read,
-	.llseek = seq_lseek,
-	.release = single_release,
-};
+DEFINE_SHOW_ATTRIBUTE(tegra_emc_debug_available_rates);
 
 static int tegra_emc_debug_min_rate_get(void *data, u64 *rate)
 {