tests: Remove calls to igt_pipe_crc_drain()

Calls to igt_pipe_crc_drain + get_single are already replaced with
igt_pipe_crc_get_current() in patch
https://patchwork.freedesktop.org/patch/240651/?series=47129&rev=1


so removing igt_pipe_crc_drain() shouldn't matter since tests are using
igt_pipe_crc_get_current() which will drain the old junk anyway. Its
double to do drain + get_current(), so calls to drain() can be removed.

Signed-off-by: Swati Sharma <swati2.sharma@intel.com>
Signed-off-by: Ramalingam C <ramalingam.c@intel.com>
Reviewed-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/319789/?series=64210&rev=1