configure: enable dri3 only for linux
configure: enable dri3 only for linux

Currently only linux can make use of dri3, so it would make sense to
enable it explicitly for the platform.
Drop a duplicated libudev check while we're at it.

v3: Properly handle dri3 and reword commit message.

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=76377
Cc: "10.1" <59f39c0db42d4479a46b02d4d2bc11120e37bb44@lists.freedesktop.org>
Signed-off-by: Emil Velikov <4c996f2f093ddd0585a556460b4cc3ba555546ef@gmail.com>
Reviewed-by: Ian Romanick <2b237cafb16dc45038e85df6c85e74e6d899eba9@intel.com>
Reviewed-by: Matt Turner <789b315743a28dd066a4ba1459c35951c291d8a6@gmail.com>

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