powerpc: Fix hard CPU IDs detection

commit 9d07bc84
"powerpc: Properly handshake CPUs going out of boot spin loop"

Would cause a miscalculation of the hard CPU ID. It removes breaking
out of the loop when finding a match with a processor, thus the "i"
used as an index in the intserv array is always incorrect

This broke interrupt on my PowerMac laptop.

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>