MIPS: generic: Update node names to avoid unit addresses

With the latest mkimage from U-Boot 2021.04, the generic defconfigs no
longer build, failing with:

/usr/bin/mkimage: verify_header failed for FIT Image support with exit code 1

This is expected after the linked U-Boot commits because '@' is
forbidden in the node names due to the way that libfdt treats nodes with
the same prefix but different unit addresses.

Switch the '@' in the node name to '-'. Drop the unit addresses from the
hash and kernel child nodes because there is only one node so they do
not need to have a number to differentiate them.

Cc: stable@vger.kernel.org
Link: https://source.denx.de/u-boot/u-boot/-/commit/79af75f7776fc20b0d7eb6afe1e27c00fdb4b9b4
Link: https://source.denx.de/u-boot/u-boot/-/commit/3f04db891a353f4b127ed57279279f851c6b4917
Suggested-by: Simon Glass <sjg@chromium.org>
Signed-off-by: Nathan Chancellor <nathan@kernel.org>
Reviewed-by: Tom Rini <trini@konsulko.com>
Signed-off-by: Thomas Bogendoerfer <tsbogend@alpha.franken.de>

MIPS: generic: Move Boston FIT image source to its own file

Move the Boston board flattened image tree source into its own file
which is concatenated into the final image tree source used to build the
flattened image tree. Separating boards into different files will help
us to avoid conflicts as boards are added.

Signed-off-by: Paul Burton <paul.burton@imgtec.com>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/16939/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>