armbian-next: qemu-uboot-arm64 and qemu-uboot-x86 new boards

- sharing most UEFI code, will replace the `virtual` one soon
- x86: patch uboot defconfig to use the `q35` machine type, not `i440fx`
  - separate x86 bootscript, due to non-uInitrd-ness of it
  - hack ramdisk load address both in u-boot source and bootscript
  - use 32-bit u-boot, not 64-bit
- grub: introduce `UEFI_GRUB=skip`, does not deploy GRUB (but does the kernel packages, etc)
- auto-enable qcow2 output for these
- works with both distro's and Armbian's kernels

config/bootscripts/boot-qemu-x86.cmd

@@ -0,0 +1,19 @@
+# do the virtio dance
+${devtype} scan
+${devtype} info
+ls virtio ${devnum}:${distro_bootpart} /boot
+
+# higher load address; the default causes the initrd to be overwritten when the bzImage is unpacked....
+setenv ramdisk_addr_r 0x8000000
+echo KERNEL LOAD ADDRESS: kernel_addr_r: ${kernel_addr_r}
+echo INITRD LOAD ADDRESS: ramdisk_addr_r: ${ramdisk_addr_r}
+
+load ${devtype} ${devnum}:${distro_bootpart} ${kernel_addr_r} /boot/vmlinuz
+# Attention, this is the raw initrd.img, NOT uInitrd for uboot/ARM
+load ${devtype} ${devnum}:${distro_bootpart} ${ramdisk_addr_r} /boot/initrd.img
+
+# boot params
+setenv bootargs root=LABEL=armbi_root ro  console=ttyS0
+
+# zboot knows how to handle bzImage...
+zboot ${kernel_addr_r} - ${ramdisk_addr_r} ${filesize}