tests: add kms_setmode

tests: add kms_setmode

Iterate through all valid/invalid crtc/connector combinations. At the
moment only clone configurations are tested as the single output cases
are tested already by testdisplay. Also from combinations where all
connectors are on the same crtc (clone-single-crtc) only those are
tested that are invalid, as I haven't found any machine that supports
these (have to be GT2 with dvo and vga output).

For configurations with one crtc per connector the FBs are per-crtc atm.

Signed-off-by: Imre Deak <imre.deak@intel.com>