rs780: hide unused gfx ports and gpp ports

rs780: hide unused gfx ports and gpp ports

Hide the unused gfx ports and gpp ports if they are not configured as hotplug.
lspci -vvv will get more accurate information under Linux,
tested on avalue/eax-785e.

Change-Id: Iaabfd362a0a01f21d0f49aa2bd2d26f9259013fb
Signed-off-by: Kerry Sheh <kerry.she@amd.com>
Signed-off-by: Kerry Sheh <shekairui@gmail.com>
Reviewed-on: http://review.coreboot.org/206
Tested-by: build bot (Jenkins)
Reviewed-by: Patrick Georgi <patrick@georgi-clan.de>