x86: delete empty functions from pci-nommu_64.c

This functions are now called conditionally on their
existence in the struct. So just delete them, instead
of keeping an empty implementation.

Signed-off-by: Glauber Costa <gcosta@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>