redhat/configs: make x86_64-rt_debug define CONFIG_PREEMPT_RT

x86_64 RT debug kernel, currently, doesn't define CONFIG_PREEMPT_RT because priority.rhel doesn't include generic-rt and generic-rt-x86 for it.

Fix it by adding the aforementioned configurations.

Signed-off-by: Wander Lairson Costa wander@redhat.com