Added forward declaration for mce_tx_signal_cb()
Added forward declaration for mce_tx_signal_cb()

Forgot it after shuffling the code to keep the
signal installation list close to signal handler.

spiiroin/mce,mlehtima/mce,maikelwever/mce,maikelwever/mce,kimmoli/mce,mikkoharju/mce,kimmoli/mce,mikkoharju/mce,kimmoli/mce,android-808/mce,maikelwever/mce,spiiroin/mce,android-808/mce,mikkoharju/mce,spiiroin/mce,maikelwever/mce,spiiroin/mce,android-808/mce,mlehtima/mce,mlehtima/mce,mlehtima/mce,mikkoharju/mce,kimmoli/mce,android-808/mce