drm/radeon: remove defined but not used 'dte_data_tahiti_le'

Fix the following gcc warning:

drivers/gpu/drm/radeon/si_dpm.c:255:33: warning: ‘dte_data_tahiti_le’
defined but not used [-Wunused-const-variable=]
 static const struct si_dte_data dte_data_tahiti_le =

Reported-by: Hulk Robot <hulkci@huawei.com>
Signed-off-by: Jason Yan <yanaijie@huawei.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>