CondFormats/EgammaObjects: add missing dependency on roottmva

The following is visible on GCC pre-4.9.0 IB: https://cmssdt.cern.ch/SDT/cgi-bin/buildlogs/slc6_amd64_gcc490/CMSSW_7_1_X_2014-02-12-1400/CondFormats/EgammaObjects

Signed-off-by: David Abdurachmanov <David.Abdurachmanov@cern.ch>