Include kernel-*-allsyms into boot-*-allsyms.img

The patch fixes the boot-*-allsyms.img of gsi_arm64-userdebug to
pack the kernel with allsyms instead of without allsyms.

Bug: 192318869
Test: build gsi_arm64-userdebug; check the kernel in boot-*-allsyms.img
Test: build gsi_x86_64-userdebug; check the kernel in boot-*-allsyms.img
Change-Id: Ic89dbe27e166d57283c7bef574d525863d20e79f