meson: fix tizonia build

meson.build was both using path to gst-omx/openmax/OMX*
headers and path to OMX headers provided by tizilheaders.pc
so this patch makes sure we only use the later.

Also bump tizonia minimum version to 0.19.0 which
is the latest release.
9 jobs for fix_tizonia_build in 19 minutes and 17 seconds (queued for 2 seconds)
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