arch: ia64: Remove rest of perfmon support

Perfmon support (used by oprofile earlier) was removed by commit
ecf5b72d ("ia64: Remove perfmon") earlier, but it missed few files
to remove/update.

Clean it up.

Suggested-by: Arnd Bergmann <arnd@kernel.org>
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
Acked-by: Robert Richter <rric@kernel.org>
Acked-by: William Cohen <wcohen@redhat.com>
Acked-by: Al Viro <viro@zeniv.linux.org.uk>
Acked-by: Thomas Gleixner <tglx@linutronix.de>