fix: bios boot order when using virtual sdcard

Makefile

@@ -50,12 +50,13 @@ vm-bios: out/airgap.iso
 		-machine pc \
 		-serial stdio \
 		-usb \
+		-usbdevice tablet \
+		-boot d \
+		-drive file=out/airgap.iso,media=cdrom \
 		-device sdhci-pci \
 		-device sd-card,drive=external \
-		-usbdevice tablet \
 		-drive id=external,if=none,format=raw,file=out/sdcard.img \
 		-display gtk,show-menubar=off,zoom-to-fit=on \
-		-cdrom "out/airgap.iso"
 
 .PHONY: vm-efi
 vm-efi: out/airgap.iso