Remove meta-intel in favour of qemux86-64 as combined target

Remove meta-intel in favour of qemux86-64 as combined target

the qemux86-64 target will build bootable media for x86 targets
(virtual and physical). Thus we do not need another config anymore.
For compatibility, do a symlink
  intel-corei7-64 -> qemux86-64
when selecting the machine.

Bug-AGL: SPEC-2931

Signed-off-by: Jan-Simon Möller <jsmoeller@linuxfoundation.org>
Change-Id: I65aab61680d982ccfb1d9146bead591a6cfd1dd3
Reviewed-on: https://gerrit.automotivelinux.org/gerrit/c/AGL/meta-agl/+/24792
Tested-by: Jenkins Job builder account <agl-jobbuilder@automotivelinux.org>
ci-image-build: Jenkins Job builder account <agl-jobbuilder@automotivelinux.org>
ci-image-boot-test: Jenkins Job builder account <agl-jobbuilder@automotivelinux.org>
Reviewed-by: Matt Ranostay <matt.ranostay@konsulko.com>