drm/radeon: rework audio option

In 3.12 I changed audio to be enabled by default,
but you still had to turn it on via xrandr.  This
was confusing to users so change it to minic the
previous behavior:

- audio option is set to -1 (auto) by default which is
  the current 3.12 behavior (audio is enabled but requires
  xrandr to turn it on).
- if audio = 1, the audio is enabled without needing
  to mess with xrandr (previous behavior)
- audio = 0 disables audio

It retains the new feature of allowing the user to enable
audio on the fly with xrandr, but turns audio on
automatically if radeon.audio=1 is set which is what
most users expect.

Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Reviewed-by: Christian König <christian.koenig@amd.com>

drivers/gpu/drm/radeon/radeon_drv.c

@@ -153,7 +153,7 @@ int radeon_benchmarking = 0;
 int radeon_testing = 0;
 int radeon_connector_table = 0;
 int radeon_tv = 1;
-int radeon_audio = 1;
+int radeon_audio = -1;
 int radeon_disp_priority = 0;
 int radeon_hw_i2c = 0;
 int radeon_pcie_gen2 = -1;
@@ -196,7 +196,7 @@ module_param_named(connector_table, radeon_connector_table, int, 0444);
 MODULE_PARM_DESC(tv, "TV enable (0 = disable)");
 module_param_named(tv, radeon_tv, int, 0444);
 
-MODULE_PARM_DESC(audio, "Audio enable (1 = enable)");
+MODULE_PARM_DESC(audio, "Audio enable (-1 = auto, 0 = disable, 1 = enable)");
 module_param_named(audio, radeon_audio, int, 0444);
 
 MODULE_PARM_DESC(disp_priority, "Display Priority (0 = auto, 1 = normal, 2 = high)");