x86: Introduce GDT_ENTRY_INIT(), initialize bad_bios_desc statically

Fully initialize bad_bios_desc statically instead of doing some
fields statically and some dynamically.

Suggested-by: "H. Peter Anvin" <hpa@zytor.com>
Signed-off-by: Akinobu Mita <akinobu.mita@gmail.com>
LKML-Reference: <20090809080350.GA4765@localhost.localdomain>
Signed-off-by: Ingo Molnar <mingo@elte.hu>