The following shows up in chroma_defconfig:

 CC      arch/powerpc/sysdev/scom.o
arch/powerpc/sysdev/scom.c: In function 'scom_debug_init':
arch/powerpc/sysdev/scom.c:182:36: error: 'powerpc_debugfs_root' undeclared (first use in this function)
arch/powerpc/sysdev/scom.c:182:36: note: each undeclared identifier is reported only once for each function it appears in
make[2]: *** [arch/powerpc/sysdev/scom.o] Error 1
make[1]: *** [arch/powerpc/sysdev/scom.o] Error 2

A bisect leads to commit 9ffc93f203c18a70623f21950f1dd473c9ec48cd

    "Remove all #inclusions of asm/system.h"

Add the debug header which contains powerpc_debugfs_root.

Acked-by: David Howells <dhowells@redhat.com>
Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>

With module.h being implicitly everywhere via device.h, the absence
of explicitly including something for EXPORT_SYMBOL went unnoticed.
Since we are heading to fix things up and clean module.h from the
device.h file, we need to explicitly include these files now.

Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>

SCOM is a side-band configuration bus implemented on some processors.
This code provides a way for code to map and operate on devices via
SCOM, while the details of how that is implemented is left up to a
SCOM "controller" in the platform code.

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: Michael Ellerman <michael@ellerman.id.au>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>