Fix Clang compile error.

Fix Clang compile error.

cras_client_get_first_dev_type_idx returns a value less than zero on error.
pin_device_ should be an int to handle this.

BUG=468639
TEST=Build Chrome with Clang.

Committed: https://crrev.com/a2771c3a51b23179100db4084c80d7e8e54a9fe1
Cr-Commit-Position: refs/heads/master@{#336061}

[chinyue, 2015-06-16 09:22:41]

chinyue@chromium.org changed reviewers:
+ dnicoara@chromium.org

[chinyue, 2015-06-17 05:35:50]

chinyue@chromium.org changed reviewers:
+ mfoltz@chromium.org

[mark a. foltz, 2015-06-17 23:13:47]

lgtm

[chinyue, 2015-06-18 00:31:02]

The CQ bit was checked by chinyue@chromium.org

[commit-bot: I haz the power, 2015-06-18 00:35:20]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1183383002/1

[commit-bot: I haz the power, 2015-06-18 00:47:17]

The CQ bit was unchecked by commit-bot@chromium.org

[commit-bot: I haz the power, 2015-06-18 00:47:19]

Try jobs failed on following builders:
  chromium_presubmit on tryserver.chromium.linux (JOB_FAILED,
http://build.chromium.org/p/tryserver.chromium.linux/builders/chromium_presub...)

[chinyue, 2015-06-18 01:56:51]

chinyue@chromium.org changed reviewers:
+ tommi@chromium.org

[chinyue, 2015-06-18 01:57:30]

On 2015/06/18 00:47:19, commit-bot: I haz the power wrote:
> Try jobs failed on following builders:
>   chromium_presubmit on tryserver.chromium.linux (JOB_FAILED,
>
http://build.chromium.org/p/tryserver.chromium.linux/builders/chromium_presub...)

Need OWNERS approval!

[chinyue, 2015-06-23 05:33:04]

chinyue@chromium.org changed reviewers:
+ miu@chromium.org

[chinyue, 2015-06-24 07:32:53]

Hi miu, tommi,

Could you please take a look, thanks!

[miu, 2015-06-24 19:34:23]

lgtm, but it's really odd that cras_client_get_first_dev_type_idx() returns an
int, while cras_client_add_pinned_stream() takes a uint32 argument.  This is yet
another example why it's generally bad practice to use unsigned int types... 
;-)

[chinyue, 2015-06-25 01:08:01]

The CQ bit was checked by chinyue@chromium.org

[commit-bot: I haz the power, 2015-06-25 01:08:54]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1183383002/1

[commit-bot: I haz the power, 2015-06-25 01:18:11]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-06-25 01:19:10]

Patchset 1 (id:??) landed as
https://crrev.com/a2771c3a51b23179100db4084c80d7e8e54a9fe1
Cr-Commit-Position: refs/heads/master@{#336061}