tc: fix debian hwr rendering

Debian builds linux with make for 5.15 and with kleaf for 6.1
This means that for kleaf builds, the mali kernel driver is already
built during linux build, and the output just needs to be copied instead.

Now copying dma-buf-test-exporter.ko all the time, as the config
DMA_SHARED_BUFFER_TEST_EXPORTER is enabled in the kernel by default and
it is expected to be present during runtime.

Signed-off-by: Alex Dobrescu <alex.dobrescu@arm.com>