Patch from Russ Dill

The oprofile init code was broken in commit c6b9da. The new logic will
always return -ENODEV. This fixes oprofile_arch_init to return 0 on
success, and return the return value of spec->init() if applicable.
Signed-off-by: Russ Dill <Russ.Dill@gmail.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>