Corerctly sets frame type in the 2 pass case

This patch sets frame types correctly in the new
vp9_get_second_pass_params() function called prior
to encode_frame_to_data_rate() function, so that the
latter function can just work with what is passed to
it. This will allow multiple vp9_get_second_pass_params()
to be created for various encode strategies without
messing with the core encode function.

There is no difference in derf and yt. stdhd/hd are pending.

Change-Id: I70dfb97e9f497e9cee04052e0e8e0c2892eab0c3