Add kernel 6.1.21

[OrangeDog]

Used by Raspberry Pi OS 2023-05-03.

[OrangeDog]

For reference, I tried building it myself and got this error

  LD      .tmp_vmlinux.kallsyms1
arm-linux-gnueabihf-ld: arch/arm/mm/proc-syms.o:(___ksymtab+arm926_dma_clean_range+0x0): undefined reference to `arm926_dma_clean_range'
arm-linux-gnueabihf-ld: arch/arm/mm/proc-syms.o:(___ksymtab+arm926_dma_inv_range+0x0): undefined reference to `arm926_dma_inv_range'
make[1]: *** [scripts/Makefile.vmlinux:34: vmlinux] Error 1
make[1]: Target '__default' not remade because of errors.

[dhruvvyas90]

Interesting, I will take a look.

[mendhak]

Same for the 2023-10-10 images. So I think this kernel would help with images based on Debian Bookworm.

[OrangeDog]

The latest kernel being used is now 6.6.20.

[powerCord154]

I was able to fix this error my replacing arm926_dma_inv_range: and arm926_dma_clean_range: in file arch/arm/mm/proc-arm926.S with ENTRY(arm926_dma_inv_range) and ENTRY(arm926_dma_clean_range). I was able to compile the image without errors after that. It's probably an old method of defining entries that hasn't been changed in newer kernel revisions yet.