platform/x86: dell-smbios: Add filtering support

platform/x86: dell-smbios: Add filtering support

When a userspace interface is introduced to dell-smbios filtering
support will be used to make sure that userspace doesn't make calls
deemed unsafe or that can cause the kernel drivers to get out of
sync.

A blacklist is provided for the following:
- Items that are in use by other kernel drivers
- Items that are deemed unsafe (diagnostics, write-once, etc)
- Any items in the blacklist will be rejected.

Following that a whitelist is provided as follows:
- Each item has an associated capability.  If a userspace interface
  accesses this item, that capability will be tested to filter
  the request.
- If the process provides CAP_SYS_RAWIO the whitelist will be
  overridden.

When an item is not in the blacklist, or whitelist and the process
is run with insufficient capabilities the call will be rejected.

Signed-off-by: Mario Limonciello <mario.limonciello@dell.com>
Reviewed-by: Edward O'Callaghan <quasisec@google.com>
Signed-off-by: Darren Hart (VMware) <dvhart@infradead.org>