drm/radeon: re-enable dpm by default on BTC

This patch depends on:
e0792981
(drm/radeon/dpm: fix typo in vddci setup for eg/btc)

bugs:
https://bugs.freedesktop.org/show_bug.cgi?id=73053
https://bugzilla.kernel.org/show_bug.cgi?id=68571



Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Cc: stable@vger.kernel.org