media: tc358743: Increase FIFO level to 374.

The existing fixed value of 16 worked for UYVY 720P60 over
2 lanes at 594MHz, or UYVY 1080P60 over 4 lanes. (RGB888
1080P60 needs 6 lanes at 594MHz).
It doesn't allow for lower resolutions to work as the FIFO
underflows.

374 is required for 1080P24-30 UYVY over 2 lanes @ 972Mbit/s, but
>374 means that the FIFO underflows on 1080P50 UYVY over 2 lanes
@ 972Mbit/s.

Signed-off-by: Dave Stevenson <dave.stevenson@raspberrypi.org>