evdi 1.6.0+dfsg-1ubuntu3 ADT test failure with linux-5.8 5.8.0-1.2

[Impact]
evdi-dkms won't build with later kernels than 5.5. In some cases (upstream version 1.7.0), it won't build specifically on ppc64el. The fix includes a missing header that is indirectly included on other arches.

[Test case]
Install the package with a 5.8 kernel. Install linux-headers-5.8.0-12-generic and evdi-dkms. Check that the dkms has built for the 5.8 kernel, at /lib/modules/5.8.0-12-generic/updates/dkms/evdi.ko.

[Regression potential]
Updates to dkms packages can break the modules. They could build ok, but not load successfully. And even after loaded just fine, they can stop providing the correct functionality, or introduce new bugs.

[Other info]
This has been tested to build and load on a ppc64el system running linux 5.8.0-12-generic and also 5.4.0-37-generic.

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Testing failed on:
    amd64: https://objectstorage.prodstack4-5.canonical.com/v1/AUTH_77e2ada1e7a84929a74ba3b87153c0ac/autopkgtest-groovy-canonical-kernel-team-bootstrap/groovy/amd64/e/evdi/20200619_205539_4b87a@/log.gz
    arm64: https://objectstorage.prodstack4-5.canonical.com/v1/AUTH_77e2ada1e7a84929a74ba3b87153c0ac/autopkgtest-groovy-canonical-kernel-team-bootstrap/groovy/arm64/e/evdi/20200619_211747_a93df@/log.gz
    armhf: https://objectstorage.prodstack4-5.canonical.com/v1/AUTH_77e2ada1e7a84929a74ba3b87153c0ac/autopkgtest-groovy-canonical-kernel-team-bootstrap/groovy/armhf/e/evdi/20200619_210243_40fa8@/log.gz
    ppc64el: https://objectstorage.prodstack4-5.canonical.com/v1/AUTH_77e2ada1e7a84929a74ba3b87153c0ac/autopkgtest-groovy-canonical-kernel-team-bootstrap/groovy/ppc64el/e/evdi/20200619_205911_3fda4@/log.gz
    s390x: https://objectstorage.prodstack4-5.canonical.com/v1/AUTH_77e2ada1e7a84929a74ba3b87153c0ac/autopkgtest-groovy-canonical-kernel-team-bootstrap/groovy/s390x/e/evdi/20200619_205610_b6afa@/log.gz