Add initial j7-evm machine support

Add initial j7-evm machine support

Add template and inc file for requested j7-evm machine.

Notes:
- The various images have been test built, including the
  agl-demo-platform image.  No runtime testing has been done due to
  lack of hardware.
- The proprietary SGX graphics support has not been enabled.  This
  is due to both being unable to test, and it being unclear if it
  is required given the telematics usecases mentioned with respect
  to the hardware.
- The shared TMPDIR for the non-optional multiconfig for building
  the bootloader has been shifted to a split one, as failures were
  reproducibly being seen when using the rm_work bbclass, and in
  general the community recommendation is to not share them.  This
  does mean that cleaning up a build tree requires removing the
  tmp-k3r5 directory in addition to tmp.

Bug-AGL: SPEC-3928

Signed-off-by: Scott Murray <scott.murray@konsulko.com>
Change-Id: I5c4e325b0b709b6571946475bf128bc25b171f6e
Reviewed-on: https://gerrit.automotivelinux.org/gerrit/c/AGL/meta-agl/+/26379
Tested-by: Jenkins Job builder account
ci-image-build: Jenkins Job builder account
ci-image-boot-test: Jenkins Job builder account
Reviewed-by: Jan-Simon Moeller <jsmoeller@linuxfoundation.org>