Bluetooth: ath3k: Avoid duplication of code

In commit 86e09287, to reduce memory
usage, the functions of the ath3k module were rewritten to release the
firmware blob after it has been loaded (successfully or not).

The resuting code has some redundancy and the compiler can potentially
produce better code if we omit a function call that is unconditionally
executed in

,----
|     if (ath3k_load_firmware(udev, firmware)) {
|             release_firmware(firmware);
|             return -EIO;
|     }
|     release_firmware(firmware);
|
|     return 0;
| }
`----

It may also be argued that the rewritten code becomes easier to read,
and also to see the code coverage of the snippet in question.

Signed-off-by: Rogério Brito <rbrito@ime.usp.br>
Cc: Alexander Holler <holler@ahsoftware.de>
Cc: "Gustavo F. Padovan" <padovan@profusion.mobi>
Cc: Miguel Ojeda <miguel.ojeda.sandonis@gmail.com>
Signed-off-by: Gustavo F. Padovan <padovan@profusion.mobi>