[coreboot] No CBMEM console available for QEMU

[Paul Menzel]

Dear coreboot folks,

building coreboot for the target QEMU x86 q35/ich9 (aka qemu -M q35,
since v1.4) I am unable to enable CBMEM console in the Kconfig menu
(`make menuconfig`).

As coreboot messages should be uploaded to the board status repository
and only CBMEM console is supported, I wonder how to accomplish that.

Thanks,

Paul