firmware: Add DMI entry types to the headers

In preparation for the upcoming commits, introduce the DMI entry types to
the headers.  These type names are based on those specified in the DMTF
SMBIOS specification version 2.7.1.

Signed-off-by: Mike Waychison <mikew@google.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>