tests/check/: Enable ffmpegcolorspace test now that the RGBA32 issue is fixed (for now not for valgrinding though, si...

Original commit message from CVS:
* tests/check/Makefile.am:
* tests/check/elements/ffmpegcolorspace.c:
(ffmpegcolorspace_suite):
Enable ffmpegcolorspace test now that the RGBA32 issue is fixed
(for now not for valgrinding though, since it takes too long).