kbuild: do not warn when unwind sections references .init/.exit sections

Andrew Morton reported a number of false positives for ia64 - like these:
WARNING: drivers/acpi/button.o - Section mismatch: reference to .init.text: from .IA_64.unwind.init.text after '' (at offset 0x0)
WARNING: drivers/acpi/button.o - Section mismatch: reference to .exit.text: from .IA_64.unwind.exit.text after '' (at offset 0x0)
WARNING: drivers/acpi/processor.o - Section mismatch: reference to .init.text: from .IA_64.unwind after '' (at offset 0x1e8)

They are all false positives - or at least the .c code looks OK.
It is not known why sometimes a section name is appended and sometimes not.

Fix is to accept references from all sections that includes "unwind." in the name.

Signed-off-by: Sam Ravnborg <sam@ravnborg.org>