msdkvpp: don't use NV12 as default output in normal mode

If so, BGRA is the preferred output format hence BGRA will be selected
as input format by default, e.g. in the pipleline below, BGRA instead of
NV12 is selected without renegotiation, so we can avoid the NV12 issue
(see commit 3f2314a1) by default.

gst-launch-1.0 videotestsrc ! msdkvpp ! glimagesink
6 jobs for master in 40 minutes and 17 seconds (queued for 1 second)
Status Job ID Name Coverage
  Preparation
passed #75632
gst indent

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passed #75631
manifest

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  Build
passed #75633
build fedora x86_64

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  Test
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check fedora

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  Full Builds
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build android arm64 api28

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build cerbero fedora x86_64

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