hidapi/linux: fix uninitialized variable

[0xilis]

In parse_hid_vid_pid_from_uevent_path, if the file is less than 1024 bytes somehow, the read() call will return the size of the file and pass the if (res < 0) check, but the leftover bytes that were not copied to from the file will remain uninitialized. This commit fixed it by initializing the buffer with 0.

[Youw]

1. I can't even recall it C supports = {0} initialisation by the standard.

2. The function ensures that the string is NULL-terminated and that buffer is always threated as a c-string, so uninitialized part of the memory would never be read. Unless you've found a an excemple where it actually fails. Did you?