i3c: master: svc: Fix npcm845 FIFO_EMPTY quirk

i3c: master: svc: Fix npcm845 FIFO_EMPTY quirk

In a private write transfer, the driver pre-fills the FIFO to work around
the FIFO_EMPTY quirk. However, if an IBIWON event occurs, the hardware
emits a NACK and the driver initiates a retry. During the retry, driver
attempts to pre-fill the FIFO again if there is remaining data, but since
the FIFO is already full, this leads to data loss.

Check available space in FIFO to prevent overflow.

Fixes: 4008a74e0f9b ("i3c: master: svc: Fix npcm845 FIFO empty issue")
Signed-off-by: Stanley Chu <yschu@nuvoton.com>
Link: https://lore.kernel.org/r/20250730003719.1825593-1-yschu@nuvoton.com
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>