drm/vmwgfx: Clean up some debug messages in vmwgfx_execbuf.c

Now that vmw_cmd_check prints debug message whenever a command verifier
fails, some of debug statements are unnecessary. Also rearranged some
debug print-out with this patch.

Signed-off-by: Deepak Rawat <drawat@vmware.com>
Reviewed-by: Thomas Hellstrom <thellstrom@vmware.com>