platform/x86: samsung-laptop: set debugfs blobs to read only

Those blobs can only be read. So, don't confuse users with 'writable'
flags. Also, remove S_IFREG because debugfs takes care of that.

Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Signed-off-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Link: https://lore.kernel.org/r/20210517100746.29663-2-wsa+renesas@sang-engineering.com


Signed-off-by: Hans de Goede <hdegoede@redhat.com>