build/roms: remove modify_coreboot_rom()

don't handle "romtype" at all, in board target.cfg files

add /dev/null as pike2008 rom on amd boards. this serves
the same purpose, adding them as empty vga roms, to add
an empty rom in cbfs. pike2008 cards cause seabios to hang,
when their oproms are executed, so we insert a fake rom

on i945 thinkpads, use the coreboot config option:
CONFIG_INTEL_ADD_TOP_SWAP_BOOTBLOCK

when set, this enables the same bootblock copy, for use
with bucts. these two cases, namely pike2008 roms and
i945 bootblock copies, no longer need to be handled in code

Signed-off-by: Leah Rowe <leah@libreboot.org>

script/vendor/download

@@ -94,6 +94,7 @@ fetch()
 	dl="${2}"
 	dl_bkup="${3}"
 	dlsum="${4}"
+	[ "${5}" = "/dev/null" ] && return 0
 	[ "${5# }" = "${5}" ] || err "fetch: space not allowed in _dest: '${5}'"
 	[ "${5#/}" = "${5}" ] || err "fetch: absolute path not allowed: '${5}'"
 	_dest="${5##*../}"