LoongArch Adds ACPI BGRT Support & Other Improvements For Linux 6.12

The LoongArch architecture support for these Chinese processors continue seeing better support with the upstream Linux kernel.

The LoongArch CPU port updates for the Linux 6.12 kernel have been merged. Among the changes are adding ACPI Boot Graphics Record Table (BGRT) for LoongArch to enjoy the better Plymouth boot splash screen integration for systems/motherboards having a logo to display as part of the boot process. LoongArch also now supports Linux's generic CPU vulnerabilities reporting infrastructure.

The LoongArch port also now sets the ARCH_HAS_SET_MEMORY and ARCH_HAS_SET_DIRECT_MAP kernel features, improves its hardware page table walker, and other changes.

1, Fix objtool about do_syscall() and Clang;
2, Enable generic CPU vulnerabilites support;
3, Enable ACPI BGRT handling;
4, Rework CPU feature probe from CPUCFG/IOCSR;
5, Add ARCH_HAS_SET_MEMORY support;
6, Add ARCH_HAS_SET_DIRECT_MAP support;
7, Improve hardware page table walker;
8, Simplify _percpu_read() and _percpu_write();
9, Add advanced extended IRQ model [documentation];
10, Some bug fixes and other small changes.

More details on the LoongArch changes for Linux 6.12 via the pull request.