mediafoundation: Fix for UWP build

We don't support D3D11 interop for UWP because some APIs
(specifically MFTEnum2) are desktop application only.
However, the code for symbol loading is commonly used by both UWP and WIN32.
Just link GModule unconditionally which is UWP compatible, and simply don't
try to load any library/symbol dynamically when D3D11 interop is unavailable.

Part-of: <gstreamer/gstreamer!1216>
23 jobs for !1216 with mf-uwp-build in 33 minutes and 19 seconds (queued for 15 seconds)
detached
Status Name Job ID Coverage
  Trigger
passed trigger #14966234

00:00:08

 
  Build Docker
passed fedora amd64 docker #14966235

00:00:19

passed gst-indent amd64 docker #14966236

00:00:17

passed windows amd64 docker #14966237
windows shell 1809

00:00:11

 
  Preparation
passed gst indent #14966238

00:00:24

 
  Build
passed build clang fedora x86_64 #14966242

00:09:23

passed build documentation #14966246

00:11:47

manual build msys2 #14966245
docker windows 1809 allowed to fail manual
passed build nodebug fedora x86_64 #14966239

00:06:13

passed build static fedora x86_64 #14966240

00:07:00

passed build static nodebug fedora x86_64 #14966241

00:04:55

passed build vs2017 amd64 #14966243
docker windows 1809

00:07:40

passed build vs2017 x86 #14966244
docker windows 1809

00:08:54

passed cerbero trigger #14966247

00:31:59

 
  Test
passed check fedora #14966248
gstreamer

00:07:38

passed integration testsuites fedora 1/4 #14966249
gstreamer

00:32:32

passed integration testsuites fedora 2/4 #14966250
gstreamer

00:30:40

passed integration testsuites fedora 3/4 #14966251
gstreamer

00:30:36

passed integration testsuites fedora 4/4 #14966252
gstreamer

00:31:16

passed valgrind bad #14966253
gstreamer

00:09:27

passed valgrind ges #14966254
gstreamer

00:06:00

 
  Integrate
passed gstreamer-full #14966255

00:05:16

passed gstreamer-full-minimal #14966256

00:05:44