qemu_process.c: adding maxCpus value to error message

qemu_process.c: adding maxCpus value to error message

Adding the maxCpus value in the error message of qemuValidateCpuCount
allows the user to set an acceptable maxCpus count without knowing
QEMU internals.

x86 guests, that might have been created prior to the x86
qemuDomainDefValidate maxCpus check code (that validates the maxCpus value
in editing time), will also benefit from this change.

Signed-off-by: Daniel Henrique Barboza <danielhb413@gmail.com>
Reviewed-by: John Ferlan <jferlan@redhat.com>