Bluetooth: Controller: Recent RAM usage increase for hci_rpmsg build

[Thalley]

Is your enhancement proposal related to a problem? Please describe.
Recently the file ull_llcp.c file was added, which increased the RAM usage of the hci_rpmsg sample by roughly 4500 bytes. The result of this is that CONFIG_BT_CTLR_SYNC_ISO and CONFIG_BT_CTLR_ADV_ISO can no longer fit in RAM for the sample anymore.

Describe the solution you'd like
Since the hci_rpmsg is a sample that makes it possible to use the nRF5340 across multiple cores (app and net core), it is imperative that it is possible to build a general-use controller build with that sample. It should be possible to use the hci_rpmsg with extended advertising and ISO support (both connected and broadcast).

Describe alternatives you've considered
N/A

Additional context
I've attached logs of a recent commit (53f2ccf2a2f587882503e4eece00fa871a9492d5) and an older (pre ull_llcp.c) commit (c3302d5f41c9f17775f4c69a5baa9e8c72f9cf3d) that shows the increase in memory. The logs files are from building hci_rpmsg with CONFIG_BT_EXT_ADV=y, CONFIG_BT_PER_ADV_SYNC=y and CONFIG_BT_CTLR_SYNC_ISO=y.

ram_53f2ccf2a2f587882503e4eece00fa871a9492d5.txt
ram_c3302d5f41c9f17775f4c69a5baa9e8c72f9cf3d.txt

[Thalley]

ping @cvinayak @kruithofa @wopu-ot

[Thalley]

I also created #49623 so that we can track the (vanilla) edition of the sample on the nRF5340 netcore.

[wopu-ot]

We are seeing an increase in memory consumption for our platform as well. ping @erbr-ot

[ppryga-nordic]

@Thalley does it mean that with enabled ISO (and other required features) the sample is about edge of free memory for nRF5340 net core?

[Thalley]

@Thalley does it mean that with enabled ISO (and other required features) the sample is about edge of free memory for nRF5340 net core?

It actually goes over the edge if I enable both CONFIG_BT_CTLR_SYNC_ISO and CONFIG_BT_CTLR_ADV_ISO (so that is excluding support for connected ISO).

Vinayak has also pointed out that by default the BT_CONN_MAX is 16 for this build, so some memory can be free'd if I lower that value.

[kruithofa]

RAM usage for vanilla hci-rpmsg sample was reduced, but there is still a significant memory usage for the hci-rpmsg sample with both sync receiver and broadcast source enabled

[kruithofa]

Increased RAM usage is pretty much a result of added functionality.
Adjusting parameters (like reducing max. nr. of connections) will help.