Blackfin: update ftrace for latest toolchain

The mcount support that was finally added to the Blackfin gcc port isn't
exactly the same as what ftrace was developed against.  Now that the final
gcc version is in place, update the ftrace code to match.

While updating this, fix the swapped arguments to the tracer (signature is
(ip, parent_ip) while we were passing (parent_ip, ip)).

Signed-off-by: Yi Li <yi.li@analog.com>
Signed-off-by: Mike Frysinger <vapier@gentoo.org>