Due to the recent changes with the formality checks kernel_bump commit
messages no-longer pass them.
Adjust these messages to follow the updated checks:
- start the first word after prefix with lower-case
- reduce the overall subject length by removing the redundant 'kernel'
Signed-off-by: George Sapkin <george@sapk.in>
Link: https://github.com/openwrt/openwrt/pull/21012
Signed-off-by: Hauke Mehrtens <hauke@hauke-m.de>
