drm/radeon: fix runpm handling on APUs (v4)

Don't try and runtime suspend the APU in PX systems.  We
only want to power down the dGPU.

v2: fix harder
v3: fix stupid typo
v4: consolidate runpm enablement to a single flag

bugs:
https://bugs.freedesktop.org/show_bug.cgi?id=75127
https://bugzilla.kernel.org/show_bug.cgi?id=72701

Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Cc: stable@vger.kernel.org
diff --git a/drivers/gpu/drm/radeon/radeon_family.h b/drivers/gpu/drm/radeon/radeon_family.h
index 614ad54..9da5da4 100644
--- a/drivers/gpu/drm/radeon/radeon_family.h
+++ b/drivers/gpu/drm/radeon/radeon_family.h
@@ -115,6 +115,7 @@
 	RADEON_NEW_MEMMAP = 0x00400000UL,
 	RADEON_IS_PCI = 0x00800000UL,
 	RADEON_IS_IGPGART = 0x01000000UL,
+	RADEON_IS_PX = 0x02000000UL,
 };
 
 #endif