arch: powerpc: Remove oprofile

The previous commit already disabled building oprofile, lets remove the
oprofile directory now.

Suggested-by: Christoph Hellwig <[email protected]>
Suggested-by: Linus Torvalds <[email protected]>
Signed-off-by: Viresh Kumar <[email protected]>
Acked-by: Robert Richter <[email protected]>
Acked-by: William Cohen <[email protected]>
Acked-by: Al Viro <[email protected]>
Acked-by: Thomas Gleixner <[email protected]>

Author: vireshk