drm/radeon/pm: fix multi-head profile handling on BTC+ (v2)

Starting on BTC, there are no longer separate states for
single head and multi-head, we just use the high mclk/voltage
for all states for multi-head.

Fixes:
https://bugs.freedesktop.org/show_bug.cgi?id=49981



v2: fix typo

Signed-off-by: Alex Deucher <alexander.deucher@amd.com>