efinitions of u32, mode_t, and so on.
 - forward declaring struct file_operations.
 - including <linux/err.h> when CONFIG_DEBUG_FS is not set

The last change is particularly useful, as a kernel developer is
likely to build with debugfs always enabled and never see the build
breakage cased if debugfs is disabled.

Signed-off-by: Roland Dreier <roland@topspin.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

¹STn—&x