riscv: zicbom extension support

[br]

Summary

Detect zicbom extension and install cache invalidation handlers

Test Plan

The extension found on Codasip X730 and required by AXI DMA engine driver

[jrtc27]

sys/conf/kern.mk

166 ↗

(On Diff #153732)

You shouldn't just do that unconditionally. Just .option push; .option arch, +zicbom ... .option pop in asm that needs it.

sys/riscv/riscv/cbo.c

48

0 can be dropped for all these, and does the singular operand really need to be named? %0 is fine, surely?

sys/riscv/riscv/identcpu.c

228–229

Obsolete?

354–357

OF_getencprop can fail. But also why not just pass sizeof(desc->foo) and let it check the length for you?

[br]

Address @jrtc27 comments.

[br]

Remove 0

[br]

handle return code of OF_getencprop() correctly