libstagefright: Do not use max/min luminance if it's 0

this changes is from following commits for ACodec.
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Do not set SMPTE2086 if max/min luminance fields are 0,
these may indicate that max/min luminance is not present
in the bitstream. Let GPU composition use default if needed.

Bug: 153847809
Test: Play Netflix HDR content in GPU composition.
Change-Id: Ibce5319f7832095314fe07b0ce13600658ce4627
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Change-Id: I41113317e31ee30ed0d093d1fd57662110f798b2
Signed-off-by: Taehwan Kim <t_h.kim@samsung.com>