sna: Fix the relocation dword for stippled_1_blt

We were telling the kernel the correct location for it to fill the
64b relocation, but we were writing the presumed offset into the wrong
pair of dwords in the batch ourselves. For the frequent case where we
used a new upload buffer, the kernel would perform the fixup and correct
our mistake, but if we happened to reuse a buffer then we told the gpu
to source the stipple from the wrong address.

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=105886


Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>