Fix OMXCodec members order, resolve warning in libstagefright initializer

See media/libstagefright/OMXCodec.cpp L 1492 OMXCodec:OMXCode()

Last change related to this code was about optimisation for 7x30 : b6967760

Signed-off-by: Tanguy Pruvot <tanguy.pruvot@gmail.com>

Change-Id: Ic0d7700df6fb401b3ef64a11ea71a4e735cc42b5