coccinelle: device_attr_show: Adapt to the latest Documentation/filesystems/sysfs.rst

Adapt description, warning message and MODE=patch according to the latest
Documentation/filesystems/sysfs.rst:
> show() should only use sysfs_emit() or sysfs_emit_at() when formatting
> the value to be returned to user space.

After this patch:
When MODE=report,
 $ make coccicheck COCCI=scripts/coccinelle/api/device_attr_show.cocci M=drivers/hid/hid-picolcd_core.c MODE=report
 <...snip...>
 drivers/hid/hid-picolcd_core.c:304:8-16: WARNING: please use sysfs_emit or sysfs_emit_at
 drivers/hid/hid-picolcd_core.c:259:9-17: WARNING: please use sysfs_emit or sysfs_emit_at

When MODE=patch,
 $ make coccicheck COCCI=scripts/coccinelle/api/device_attr_show.cocci M=drivers/hid/hid-picolcd_core.c MODE=patch
 <...snip...>
 diff -u -p a/drivers/hid/hid-picolcd_core.c b/drivers/hid/hid-picolcd_core.c
 --- a/drivers/hid/hid-picolcd_core.c
 +++ b/drivers/hid/hid-picolcd_core.c
 @@ -255,10 +255,12 @@ static ssize_t picolcd_operation_mode_sh
  {
         struct picolcd_data *data = dev_get_drvdata(dev);

 -       if (data->status & PICOLCD_BOOTLOADER)
 -               return snprintf(buf, PAGE_SIZE, "[bootloader] lcd\n");
 -       else
 -               return snprintf(buf, PAGE_SIZE, "bootloader [lcd]\n");
 +       if (data->status & PICOLCD_BOOTLOADER) {
 +               return sysfs_emit(buf, "[bootloader] lcd\n");
 +       }
 +       else {
 +               return sysfs_emit(buf, "bootloader [lcd]\n");
 +       }
  }

  static ssize_t picolcd_operation_mode_store(struct device *dev,
 @@ -301,7 +303,7 @@ static ssize_t picolcd_operation_mode_de
  {
         struct picolcd_data *data = dev_get_drvdata(dev);

 -       return snprintf(buf, PAGE_SIZE, "hello world\n");
 +       return sysfs_emit(buf, "hello world\n");
  }

  static ssize_t picolcd_operation_mode_delay_store(struct device *dev,

CC: Julia Lawall <Julia.Lawall@inria.fr>
CC: Nicolas Palix <nicolas.palix@imag.fr>
CC: cocci@inria.fr
Signed-off-by: Li Zhijian <lizhijian@fujitsu.com>