I couldn't think of a reason why we would need to unset the CRTCs
before doing the modesets on this test, so remove all the mode unset
calls.

Before:
$ time -p sudo ./kms_draw_crc
real 44.74
$ time -p for i in $(sudo ./kms_draw_crc --list-subtests); do sudo
./kms_draw_crc --run-subtest $i; done
real 121.61

After:
$ time -p sudo ./kms_draw_crc
real 7.40
$ time -p for i in $(sudo ./kms_draw_crc --list-subtests); do sudo
./kms_draw_crc --run-subtest $i; done
real 14.32

Signed-off-by: Paulo Zanoni <paulo.r.zanoni@intel.com>