Do not ignore the fifo_size parameter in the st30p tx pipeline api (#948)

[hogliux]

The st30p pipeline API allows the user to specify the fifo_size parameter. Unfortunately, the parameter is ignored and not used anywhere in the codebase. This parameter is critical for achieving low latency audio streams.

See issue #948

[Sakoram]

Again, due to temporary infrastructure problems, I ran the unit tests locally. They passed successfully:
Running test: ===========================================
./build/tests/KahawaiUfdTest --p_port 0000:4b:01.1 --r_port 0000:4b:01.2

Test passed in 16 seconds.

===========================================
Running test: ===========================================
./build/tests/KahawaiUfdTest --p_port 0000:4b:01.1 --r_port 0000:4b:01.2 --queue_mode shared

Test passed in 20 seconds.

===========================================
Running test: ===========================================
./build/tests/KahawaiUfdTest --p_port 0000:4b:01.1 --r_port 0000:4b:01.2 --queue_mode shared --udp_lcore

Test passed in 20 seconds.

===========================================
Running test: ===========================================
./build/tests/KahawaiUfdTest --p_port 0000:4b:01.1 --r_port 0000:4b:01.2 --rss_mode l3_l4

Test passed in 18 seconds.

===========================================
Running test: ===========================================
./build/tests/KahawaiTest --auto_start_stop --p_port 0000:4b:01.1 --r_port 0000:4b:01.2 --dma_dev 0000:00:01.0,0000:00:01.1 --gtest_filter=-St22_?x.*

Test passed in 776 seconds.

===========================================
Running test: ===========================================
./build/tests/KahawaiTest --auto_start_stop --p_port 0000:4b:01.1 --r_port 0000:4b:01.2 --rss_mode l3_l4 --pacing_way tsc --iova_mode pa --multi_src_port --gtest_filter=Main.:St20p:-ext

Test passed in 81 seconds.

===========================================
Running test: ===========================================
./build/tests/KahawaiTest --p_port kernel:lo --r_port kernel:lo --auto_start_stop --gtest_filter=St20p*

Test passed in 138 seconds.

===========================================

[PanKaker]

Thank you for your contribution. Looks good to me