rom.sh: disable seabios-as-primary if grub is main

on 3050micro, we disable seabios as a primary payload,
making grub a pribary payload instead.

the way it worked, the roms were still named seagrub
and the seabios rom would be compiled, but with the wrong
path, so seabios wouldn't be executed; seabios would hang
anyway, on this board.

instead, engineer it in such a way as to disable seabios_
images on this board. also, rename seagrub_ to grub_.

i normally only permit seagrub, and not grub, but i make an
exception for 3050micro because we know grub works, but seabios
currently hangs on this board (which means no bsd).

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

include/rom.sh

@@ -135,7 +135,8 @@ add_seabios()
 
 	[ "$payload_grub" = "y" ] && add_grub
 
-	cprom && [ "$payload_grub" = "y" ] && pname="seagrub" && mkseagrub; :
+	[ "$seabiosname" = "fallback/payload" ] && cprom
+	[ "$payload_grub" = "y" ] && pname="seagrub" && mkseagrub; :
 }
 
 add_grub()
@@ -149,6 +150,7 @@ add_grub()
 
 mkseagrub()
 {
+	[ "$grubname" = "fallback/payload" ] && pname="grub"
 	cbfs "$tmprom" "$grubdata/bootorder" bootorder raw
 	for keymap in config/data/grub/keymap/*.gkb; do
 		[ -f "$keymap" ] && cprom "${keymap##*/}"; :