dmi: log board, system, and BIOS information

Put basic system information in the dmesg log.  There are lots of dmesg
logs on the web, and it would be useful if they contained this information
for debugging platform problems.  "BOARD/PRODUCT" format copied from
show_regs_common(), which is used in the oops path.

Signed-off-by: Bjorn Helgaas <bjorn.helgaas@hp.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Alan Cox <alan@lxorguk.ukuu.org.uk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>