maint: avoid 'const fooPtr' in qemu

maint: avoid 'const fooPtr' in qemu

'const fooPtr' is the same as 'foo * const' (the pointer won't
change, but it's contents can).  But in general, if an interface
is trying to be const-correct, it should be using 'const foo *'
(the pointer is to data that can't be changed).

Fix up offenders in src/qemu.

* src/qemu/qemu_bridge_filter.h (networkAllowMacOnPort)
(networkDisallowMacOnPort): Use intended type.
* src/qemu/qemu_bridge_filter.c (networkAllowMacOnPort)
(networkDisallowMacOnPort): Likewise.
* src/qemu/qemu_command.c (qemuBuildTPMBackendStr)
(qemuBuildTPMDevStr, qemuBuildCpuArgStr)
(qemuBuildObsoleteAccelArg, qemuBuildMachineArgStr)
(qemuBuildSmpArgStr, qemuBuildNumaArgStr): Likewise.
* src/qemu/qemu_conf.c (qemuSharedDeviceEntryCopy): Likewise.
* src/qemu/qemu_driver.c (qemuDomainSaveImageStartVM): Likewise.
* src/qemu/qemu_hostdev.c
(qemuDomainHostdevNetConfigVirtPortProfile): Likewise.
* src/qemu/qemu_monitor_json.c
(qemuMonitorJSONAttachCharDevCommand): Likewise.

Signed-off-by: Eric Blake <eblake@redhat.com>