update seabios to latest master

Upstream seabios commit 5a023065388287e261ae9212452ff541f9fa9cd3

Major changes since 1.7.0:
 - Usual share of bugfixes and cleanups ;)
 - Support for 64bit PCI bars and mapping those above 4G.
 - Stack switching for real mode irq handlers to reduce
   seabios stack footprint.
 - Support for booting from lsi scsi hba.
 - Support for booting from usb attached scsi.
 - Support for non-linear apic ids.

Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>