Feature/add ssr

[fingercracker]

• add ssr_fpga.c, stub out read and write functions so as to allow for registration of ssr and successful building
• add minimal version of ssr_fpga.h
• add minimal version of qemu_ssr_fpga_interface.cpp -- only includes the init function
• update Dockerfile with unlimited concurrency for make builds of fsw code
• update the meson.build file in hw/sparc/ accordingly to reflect new files added

[github-actions]

Thank you for your interest in the QEMU project.

This repository is a read-only mirror of the project's repostories hosted
on https://gitlab.com/qemu-project/qemu.git.
The project does not process merge requests filed on GitHub.

QEMU welcomes contributions of code (either fixing bugs or adding new
functionality). However, we get a lot of patches, and so we have some
guidelines about contributing on the project website:
https://www.qemu.org/contribute/