nodedev: fix build with clang
nodedev: fix build with clang

Build fails with:

conf/node_device_conf.c:825:62: error: comparison of unsigned enum expression < 0 is always false [-Werror,-Wtautological-compare]
    if ((data->drm.type = virNodeDevDRMTypeFromString(type)) < 0) {
        ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ^ ~
conf/node_device_conf.c:1801:59: error: comparison of unsigned enum expression < 0 is always false [-Werror,-Wtautological-compare]
        if ((type = virNodeDevDevnodeTypeFromString(tmp)) < 0) {
            ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ^ ~
2 errors generated.

Fix by using intermediate variable to store the result similarly
to how it's done for other FromString* calls.

jardasgit/libvirt,VenkatDatta/libvirt,jfehlig/libvirt,andreabolognani/libvirt,jardasgit/libvirt,jfehlig/libvirt,datto/libvirt,VenkatDatta/libvirt,andreabolognani/libvirt,datto/libvirt,nertpinx/libvirt,jardasgit/libvirt,libvirt/libvirt,olafhering/libvirt,crobinso/libvirt,andreabolognani/libvirt,zippy2/libvirt,jardasgit/libvirt,fabianfreyer/libvirt,zippy2/libvirt,datto/libvirt,eskultety/libvirt,zippy2/libvirt,taget/libvirt,VenkatDatta/libvirt,fabianfreyer/libvirt,nertpinx/libvirt,olafhering/libvirt,taget/libvirt,zippy2/libvirt,crobinso/libvirt,nertpinx/libvirt,olafhering/libvirt,nertpinx/libvirt,jardasgit/libvirt,VenkatDatta/libvirt,taget/libvirt,libvirt/libvirt,fabianfreyer/libvirt,eskultety/libvirt,jfehlig/libvirt,eskultety/libvirt,eskultety/libvirt,eskultety/libvirt,andreabolognani/libvirt,libvirt/libvirt,olafhering/libvirt,andreabolognani/libvirt,libvirt/libvirt,datto/libvirt,jfehlig/libvirt,crobinso/libvirt,taget/libvirt,datto/libvirt,fabianfreyer/libvirt,nertpinx/libvirt,crobinso/libvirt,fabianfreyer/libvirt,taget/libvirt,VenkatDatta/libvirt