Linux 5.9 Dropping The Unicore 32-bit RISC Architecture

It's arguably long overdue but with the just-opened Linux 5.9 kernel cycle the Unicore32 CPU architecture is being removed.

Unicore is a 32-bit RISC architecture developed at China's Peking University. Unicore is an ARM-like architecture. But with Unicore not being too popular and this code not seeing any maintenance for the mainline kernel paired with no upstream compiler support, it's time to gut the code out of the kernel.

The Unicore32 port relied upon pre-built compiler toolchains for build support but those binaries have disappeared plus became too out-of-date for being able to build the kernel. Even upstream kernel developers once interested in Unicore32 haven't been able to do anything with building it since the late Linux 4.x days over the lack of upstream, open-source compiler support.

As such, this Linux kernel port is now dead and being removed with Linux 5.9. Clearing out the Unicore32 architecture code from the kernel lightens it up by 17.5k lines of code.