fix(PIEthernet): check open() return value with >= 0 instead of != 0

open() returns -1 on error. The check fd != 0 treated -1 as a
valid fd (since -1 != 0 is true), causing devctl(-1, ...) and
close(-1) on QNX. Fixed to fd >= 0.

libs/main/io_devices/piethernet.cpp

@@ -1234,7 +1234,7 @@ PIEthernet::InterfaceList PIEthernet::interfaces() {
 #	  ifdef QNX
 #		ifndef BLACKBERRY
 			int fd = ::open((PIString("/dev/io-net/") + ci.name).dataAscii(), O_RDONLY);
-			if (fd != 0) {
+			if (fd >= 0) {
 				nic_config_t nic;
 				devctl(fd, DCMD_IO_NET_GET_CONFIG, &nic, sizeof(nic), 0);
 				::close(fd);