d2q9: replace attribute 'unused' with 'used'

d2q9: replace attribute 'unused' with 'used'

While the attribute 'unused' only removes a warning, the
attribute 'used' actually prevents the linker from removing
the object. The objects in question are dummy objects to
prevent the linker from even trying to put anything else there.

Change the Makefile to remove the sections in question (banks 1/2/3)
from the SREC file, since they contain uninitialized data anyway.