drm: Reject getfb for multi-plane framebuffers

drm: Reject getfb for multi-plane framebuffers

getfb can only return a single plane, so reject attempts to use it with
multi-plane framebuffers.

Signed-off-by: Daniel Stone <[email protected]>
Reported-by: Daniel van Vugt <[email protected]>
Reviewed-by: Rob Clark <[email protected]>
Reviewed-by: Daniel Vetter <[email protected]>
Fixes: 308e5bcbdb10 ("drm: add an fb creation ioctl that takes a pixel format v5")
Cc: [email protected] # v3.3+
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=105518
Link: https://patchwork.freedesktop.org/patch/msgid/[email protected]