Rename overlaycall/overlaydata to overlay_call/overlay_data in RT engine

[edward-jones]

This updates the runtime engine to use overlay_call and overlay_data
in the overlay attributes instead of overlaycall and overlaydata
respectively.

[oferShinaar]

Same comment as in #32 (review)
We need an explanation before merging.
NOTE: The toolchain link on CHIPS will not be changed until we have something build

[oferShinaar]

need testing ref before merge

[edward-jones]

Okay here are steps used for testing:

Updating LLVM tool chain

The LLVM tool chain needs to be updated to use the latest overlay patch. This should be in the comrv branch at https://github.com/westerndigitalcorporation/llvm-project/tree/comrv but that branch needs to be updated based on the patches currently up for review:

• https://reviews.llvm.org/D109372
• https://reviews.llvm.org/D109371

Update to use -moverlay instead of -fcomrv in the build of the demos

The branch in this pull request should be applied. This updates the build system in the demos to use -moverlay instead of -fcomrv

• Update to use -moverlay instead of -fcomrv for overlay flag chipsalliance/riscv-fw-infrastructure#3

Use renamed attributes in this pull request

The branch in this pull request should also be applied to get the RT engine to use __attribute__((overlay_call)) and __attribute__((overlay_data)) instead of the old names.

Configure and build the cti demo

Run through the steps to build the 'cti' demo

$ cd riscv-fw-infrastructure/WD-Firmware/demo/build
$ ./config.sh

Select the cti demo, build with scons targetting eh1

$ scons -c target=eh1 && scons target=eh1

Run on the board through openocd - I'm not sure what the generic way of doing this is.

[oferShinaar]

This PR was integrated into the pre-release repo (different domain).
Once we have fully built toolchain, we will also release FW that encapsulate PR #36