The image builds for Linksys EA6350 v3, EA8300, and MR8300 currently
fail on buildbots due to the KERNEL_SIZE, as stated in commit
17b7756b5a ("ipq40xx: 5.15: add testing kernel version"). Disable
these boards for now.
Signed-off-by: Sungbo Eo <mans0n@gorani.run>