synopsys: Fix fifo allocation schema
synopsys: Fix fifo allocation schema

Recommended FIFO allocation schema includes 2 maximum endpoint sizes.
Comment suggested that this is the case while it would work according
to this description only in checked endpoints were ascending sizes.
Also two same size endpoints would be counted as one.
That is fixed by way sz is filled.

Calculation used too much modulo operation while single division was enough
to account for odd FIFO sizes.

Extra space that is evenly distributed between Bulk and control endpoints
was incorrectly calculated it could prevent allocation of ISO endpoint FIFO
when bulk endpoints existed with smaller endpoint numbers.

Minimum endpoint FIFO size is 16 32bit words, FIFO space requirement is
now observed.

hathach/tinyusb,hathach/tinyusb,hathach/tinyusb