powerpc/perf: Optimize find_alternatives_list() using binary search

This patch improves the performance of event alternative lookup by
replacing the previous linear search with a more efficient binary
search. This change reduces the time complexity for the search process
from O(n) to O(log(n)). A pre-sorted table of event values and their
corresponding indices has been introduced to expedite the search
process.

Signed-off-by: Kuan-Wei Chiu <visitorckw@gmail.com>
[mpe: Call the array "presort*ed*_event_table", minor formatting]
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://msgid.link/20231013175714.2142775-1-visitorckw@gmail.com