platform/mellanox: mlxreg-io: use sysfs_emit() instead of sprintf()

Follow the advice in Documentation/filesystems/sysfs.rst:
show() should only use sysfs_emit() or sysfs_emit_at() when formatting
the value to be returned to user space.

Signed-off-by: Ai Chao <[e-mail]>
Acked-by: Vadim Pasternak <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Reviewed-by: Ilpo Järvinen <[e-mail]>
Signed-off-by: Ilpo Järvinen <[e-mail]>

drivers/platform/mellanox/mlxreg-io.c

···
 
 	mutex_unlock(&priv->io_lock);
 
-	return sprintf(buf, "%u\n", regval);
+	return sysfs_emit(buf, "%u\n", regval);
 
 access_error:
 	mutex_unlock(&priv->io_lock);