I was able to build without these extra header search paths.

Especially, the header search path -I. in kernel Makefiles is always
suspicious; it allows the compiler to search for headers in the top of
$(srctree), where obviously no header file exists.
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>