xtensa: add NOTES section to the linker script

This section collects all source .note.* sections together in the
vmlinux image. Without it .note.Linux section may be placed at address
0, while the rest of the kernel is at its normal address, resulting in a
huge vmlinux.bin image that may not be linked into the xtensa Image.elf.

Cc: stable@vger.kernel.org
Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>