drm/i915: Treat fb->offsets[] as a raw byte offset instead of a linear offset

drm/i915: Treat fb->offsets[] as a raw byte offset instead of a linear offset

Userspace wants to treat fb->offsets[] as raw byte offsets into the gem
bo. Adjust the kernel code to match.

Cc: Ben Widawsky <[email protected]>
Cc: Jason Ekstrand <[email protected]>
Cc: Daniel Stone <[email protected]>
Link: https://patchwork.freedesktop.org/patch/msgid/[email protected]
Acked-by: Ben Widawsky <[email protected]>
Fixes: 2e2adb05736c ("drm/i915: Add render decompression support")
Signed-off-by: Ville Syrjälä <[email protected]>