[PATCH] PCDP: handle tables that don't supply baud rate

The HCDP specs (i.e., PCDP revision < 3) allow zero as a default value for
baud rate and data bits.  So if firmware doesn't supply them, let
early_serial_console_init() probe for them rather than telling it the baud
rate is zero.

Also, update the URL for the PCDP spec.

Signed-off-by: Bjorn Helgaas <bjorn.helgaas@hp.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>