OvmfPkg/Microvm: wire up serial console, drop super-io

OvmfPkg/Microvm: wire up serial console, drop super-io

Microvm has no LPC bridge, so drop the PciSioSerialDxe driver.
Use SerialDxe instead, with ioport hardcoded to 0x3f8 aka com1 aka ttyS0.

With this tianocore boots to uefi shell prompt on the serial console.
Direct kernel boot can be used too.

Ref: https://bugzilla.tianocore.org/show_bug.cgi?id=3599
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
Acked-by: Jiewen Yao <Jiewen.yao@intel.com>