Main Changes
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- In fx_media_format(), set fx_media_driver_status to FX_MEDIA_INVALID
to indicate the request originates from a format call.
- In fx_media_open(), set fx_media_driver_status to FX_MEDIA_NOT_OPEN
to indicate the request originates from an open call.
Fixed issues
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-Issue #79
Signed-off-by: Haithem Rahmani <haithem.rahmani@st.com>