Add an OpenBSD driver identifier.

Source/Core/VideoCommon/DriverDetails.cpp

@@ -32,6 +32,8 @@ const u32 m_os = OS_ALL | OS_OSX;
 const u32 m_os = OS_ALL | OS_LINUX;
 #elif __FreeBSD__
 const u32 m_os = OS_ALL | OS_FREEBSD;
+#elif __OpenBSD__
+const u32 m_os = OS_ALL | OS_OPENBSD;
 #endif
 
 static Vendor m_vendor = VENDOR_UNKNOWN;

Source/Core/VideoCommon/DriverDetails.h

@@ -17,6 +17,7 @@ enum OS
   OS_OSX = (1 << 3),
   OS_ANDROID = (1 << 4),
   OS_FREEBSD = (1 << 5),
+  OS_OPENBSD = (1 << 6),
 };
 // Enum of known vendors
 // Tegra and Nvidia are separated out due to such substantial differences