Blackfin arch: fix bugs in linker script when using upstream binutils

Fix a few problems I discovered when building a kernel with upstream CVS
binutils.

We have to add the NOTES macro to our linker script, since a kernel
built with --build-id is otherwise unable to boot.  Last time NOTES was
added, it broke things, but the definition of the macro has changed not
to rely on parts of the linker script that aren't present on Blackfin.

I also noticed that _l2_lma_start does not point into the kernel image,
but rather somewhere in L1/L2 space, which seems unintended.  Also, when
the L2 section was added to the linker script, the part following it which
computes then length of the init section was not updated.

Signed-off-by: Bernd Schmidt <bernds_cb1@t-online.de>
Signed-off-by: Bryan Wu <cooloney@kernel.org>