Revert "qemu: Support chardevs with ARM virt machines"

This reverts commit 70c9b442.

This commit breaks existing aarch64 machvirt configs with:

    <serial type='pty'>
      <target port='0'/>
    </serial>
    <console type='pty'>
      <target type='serial' port='0'/>
    </console>

Which fails with:

error: Failed to start domain fedora25-aarch64
error: internal error: process exited while connecting to monitor:
2017-06-26T13:55:34.726293Z qemu-system-aarch64: -chardev pty,id=charserial0:
char device redirected to /dev/pts/5 (label charserial0)
2017-06-26T13:55:34.782121Z qemu-system-aarch64: -device
isa-serial,chardev=charserial0,id=serial0: No 'ISA' bus found for device
'isa-serial'

src/qemu/qemu_capabilities.c

@@ -5573,11 +5573,6 @@ virQEMUCapsSupportsChardev(const virDomainDef *def,
     if ((def->os.arch != VIR_ARCH_ARMV7L) && (def->os.arch != VIR_ARCH_AARCH64))
         return true;
 
-    /* The virt machine has a PCIe bus and allows plugging in the same type of
-     * devices as x86 systems do on a PCIe bus. */
-    if (qemuDomainIsVirt(def))
-        return true;
-
     /* This may not be true for all ARM machine types, but at least
      * the only supported non-virtio serial devices of vexpress and versatile
      * don't have the -chardev property wired up. */