kbuild: ignore section mismatch warnings originating from .note section

.note* sections are ELF notes, which are typically used by external
tools to examine the kernel image.  Since this is removed from any
runtime consideration, it's OK to reference any section from a .note*
section.

Signed-off-by: Jeremy Fitzhardinge <jeremy@xensource.com>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Signed-off-by: Sam Ravnborg <sam@ravnborg.org>