powerpc/ftrace: Enable C Version of recordmcount

Selects HAVE_C_RECORDMCOUNT to use the C version of the recordmcount
intead of the old Perl Version of recordmcount.

This should improve build time. It also seems like the old Perl Version
misses some calls to _mcount that the C version finds.

Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>