radeonfb_maskpll
radeonfb_maskpll(sc, RADEON_MCLK_CNTL, 0xFFFF0000,
radeonfb_maskpll(sc, index, andmask, ormask);
void radeonfb_maskpll(struct radeonfb_softc *, uint32_t, uint32_t, uint32_t);