ASPEED video engine driver prevents Linux from booting under QEMU

[amboar]

openbmc/linux@1481a047a154 fails to boot with 5dca85c. Example invocation:

$ qemu-system-arm -M romulus-bmc \
-kernel arch/arm/boot/zImage \
-dtb arch/arm/boot/dts/aspeed-bmc-opp-romulus.dtb \
-initrd ~/env/buildroot/2017.8/rootfs.cpio.xz \
-append "console=ttyS4,115200b,8n1 debug earlyprintk" \
-nographic \
-d unimp
qemu-system-arm: Aspeed iBT has no chardev backend
aspeed_vic_write: Software interrupts unavailable. IRQs to be cleared: 0x00000000ffffffff
aspeed_vic_write: Software interrupts unavailable. IRQs to be cleared: 0x0007ffff00000000
aspeed_wdt_read: uninmplemented read at offset 0x4
aspeed_wdt_read: uninmplemented read at offset 0x4
aspeed_vic_write: Software interrupts unavailable. IRQs to be cleared: 0x00000000ffffffff
aspeed_vic_write: Software interrupts unavailable. IRQs to be cleared: 0x0007ffff00000000
aspeed_wdt_read: uninmplemented read at offset 0x4
aspeed_wdt_read: uninmplemented read at offset 0x4
aspeed_vic_write: Software interrupts unavailable. IRQs to be cleared: 0x00000000ffffffff
aspeed_vic_write: Software interrupts unavailable. IRQs to be cleared: 0x0007ffff00000000
aspeed_wdt_read: uninmplemented read at offset 0x4
aspeed_wdt_read: uninmplemented read at offset 0x4
...

[amboar]

Was missing -m 512 - turns out reserving all your memory makes it hard for the kernel to do very much. We should probably improve the default behaviour.