Some kernel options were set in both the amd64 and arm64 vyos_defconfig files, even though the shared *.config fragments also cover them or should:

CONFIG_KEXEC=y
CONFIG_KEXEC_FILE=y
CONFIG_KEXEC_SIG=y
CONFIG_CRASH_DUMP=y
CONFIG_PPTP=m
CONFIG_PPPOL2TP=m

Keeping them in each arch defconfig means a change has to be made in several places, and the arch files can drift apart. For example, the x86 defconfig had CONFIG_CRASH_DUMP is not set while the common debug fragment enabled it.

• Remove these options from both arch defconfigs.
• Add KEXEC, KEXEC_FILE and KEXEC_SIG to the existing kdump section of 90-debug.config, where CRASH_DUMP already lives.
• Leave PPTP and PPPOL2TP to 58-ppp.config, which already defines them.