i3c: master: svc: Fix npcm845 FIFO empty issue

i3c: master: svc: Fix npcm845 FIFO empty issue

I3C HW stalls the write transfer if the transmit FIFO becomes empty,
when new data is written to FIFO, I3C HW resumes the transfer but the
first transmitted data bit may have the wrong value.
Fill the FIFO in advance to prevent FIFO from becoming empty.

Reviewed-by: Frank Li <Frank.Li@nxp.com>
Signed-off-by: Stanley Chu <yschu@nuvoton.com>
Link: https://lore.kernel.org/r/20250306075429.2265183-4-yschu@nuvoton.com
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>