Use a colorspace when decoding to F16

A recent change caused us to always pass a color space
to the decoder.  A revert of that change caused us to
never pass a color space to the decoder.

In order to decode to F16 (and pass CTS tests), we
need to pass a color space on decodes to F16.  This
was the "original" behavior before the bad change
and bad revert.

Test: This will allow us to pass CTS.

BUG:33814604

Change-Id: I4e569213f9d4ff5a452149c4b2ee191bf2fe6b0e