platform/x86: dell-wmi-sysman: Make init_bios_attributes() ACPI object parsing more robust

Make init_bios_attributes() ACPI object parsing more robust:
1. Always check that the type of the return ACPI object is package, rather
   then only checking this for instance_id == 0
2. Check that the package has the minimum amount of elements which will
   be consumed by the populate_foo_data() for the attr_type

Note/TODO: The populate_foo_data() functions should also be made more
robust. The should check the type of each of the elements matches the
type which they expect and in case of populate_enum_data()
obj->package.count should be passed to it as an argument and it should
re-check this itself since it consume a variable number of elements.

Fixes: e8a60aa7 ("platform/x86: Introduce support for Systems Management Driver over WMI for Dell Systems")
Cc: Divya Bharathi <Divya_Bharathi@dell.com>
Cc: Mario Limonciello <mario.limonciello@dell.com>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Link: https://lore.kernel.org/r/20210321121607.35717-1-hdegoede@redhat.com