intel: Mark up with valgrind intrinsics to reduce false positives

In particular, declare the hidden CPU mmaps to valgrind so that it knows
about those memory regions.

v2: Add an additional VG_CLEAR for the getparam

References: https://bugs.freedesktop.org/show_bug.cgi?id=35071


Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Acked-by: Ben Widawsky <ben@bwidawsk.net>
[anholt: Ideally valgrind should just learn about the ioctls, and
         removing the clear for the non-valgrindified code feels risky.]
Reviewed-by: Eric Anholt <eric@anholt.net>