firmware: dmi: Fix permissions of product_family

This is not sensitive information like serial numbers, we can allow
all users to read it.

Fix odd alignment while we're here.

Signed-off-by: Jean Delvare <jdelvare@suse.de>
Fixes: c61872c9

 ("firmware: dmi: Add DMI_PRODUCT_FAMILY identification string")
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Reviewed-by: Mika Westerberg <mika.westerberg@linux.intel.com>
Cc: Dmitry Torokhov <dmitry.torokhov@gmail.com>
Cc: Linus Walleij <linus.walleij@linaro.org>