ALSA: pcm: oss: Fix negative period/buffer sizes

In the Linux kernel, the following vulnerability has been resolved: ALSA: pcm: oss: Fix negative period/buffer sizes The period size calculation in OSS layer may receive a negative value as an error, but the code there assumes only the positive values and handle them with size_t. Due to that, a too big value may be passed to the lower layers. This patch changes the code to handle with ssize_t and adds the proper error checks appropriately.