decklink: Fix format specifier warnings in logging v2

decklink: Fix format specifier warnings in logging v2

HRESULT is unsigned long on Windows, but the Decklink headers define
it to 'int' on Linux. Confusingly, the defines that talk about the
possible return values for it use long constants. The easy fix would
be to change the linux/LinuxCOM.h header, but that's copied from the
decklink SDK.

Change the logging to always upcast to unsigned long while printing
HRESULT for consistency across platforms.