seabios: add vga configs for bochs-display and ramfb

Both bochs-display and ramfb are devices with a simple framebuffer and
no vga emulation or text mode.  seavgabios has support for text mode
emulation (at vgabios call level), we are using that to provide some
vga compatibility support for these devices.
Signed-off-by: NGerd Hoffmann <kraxel@redhat.com>

roms/Makefile

 
-vgabios_variants := stdvga cirrus vmware qxl isavga virtio
+vgabios_variants := stdvga cirrus vmware qxl isavga virtio bochs-display ramfb
 vgabios_targets  := $(subst -isavga,,$(patsubst %,vgabios-%.bin,$(vgabios_variants)))
 pxerom_variants  := e1000 e1000e eepro100 ne2k_pci pcnet rtl8139 virtio vmxnet3
 pxerom_targets   := 8086100e 808610d3 80861209 10500940 10222000 10ec8139 1af41000 15ad07b0

roms/config.vga-bochs-display

+CONFIG_BUILD_VGABIOS=y
+CONFIG_DISPLAY_BOCHS=y
+CONFIG_VGA_PCI=y

roms/config.vga-ramfb

+CONFIG_BUILD_VGABIOS=y
+CONFIG_VGA_RAMFB=y
+CONFIG_VGA_PCI=n