tests/testdisplay.c: Remove the variable only_one_mode.
tests/testdisplay.c: Remove the variable only_one_mode.

That variable is useless, instead the variables specified_mode_num and specified_disp_id can cover all the situation.
For parameter -o, all three instances should work:

./testdisplay -o 21,4 only test the 4th mode on the connector with id 21.
./testdisplay -o 21   test all the mode lines on the connector wiht id 21.
./testdisplay -o ,4   the -o is ignored, just like -a.

Signed-off-by: Yi Sun <a7ab858552be010621b3b5c596bf4feb1309fb3c@intel.com>

dlespiau/checkmate-test-igt,tiagovignatti/intel-gpu-tools,erikarn/intel-gpu-tools,chenxianqin/intel-gpu-tools,tiagovignatti/intel-gpu-tools,erikarn/intel-gpu-tools,dlespiau/checkmate-test-igt,chenxianqin/intel-gpu-tools,erikarn/intel-gpu-tools,tiagovignatti/intel-gpu-tools,tiagovignatti/intel-gpu-tools,ChrisCummins/intel-gpu-tools,rib/intel-gpu-tools,mv0/intel-gpu-tools,mv0/intel-gpu-tools,ChrisCummins/intel-gpu-tools,ChrisCummins/intel-gpu-tools,erikarn/intel-gpu-tools,rib/intel-gpu-tools,yipdw/intel-gpu-tools,yipdw/intel-gpu-tools,rib/intel-gpu-tools,ChrisCummins/intel-gpu-tools,rib/intel-gpu-tools,mv0/intel-gpu-tools,chenxianqin/intel-gpu-tools,dlespiau/checkmate-test-igt,yipdw/intel-gpu-tools,dlespiau/checkmate-test-igt,mv0/intel-gpu-tools,yipdw/intel-gpu-tools,chenxianqin/intel-gpu-tools