toolchain-external-codescape-img-mips: new package

toolchain-external-codescape-img-mips: new package

This commit adds a new package for the Codescape IMG external toolchain
for the MIPS architecture.

The legacy implementation is removed.

The Codescape hacks for IMG and MTI are duplicated.

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Signed-off-by: Romain Naour <romain.naour@gmail.com>
Signed-off-by: Arnout Vandecappelle (Essensium/Mind) <arnout@mind.be>
Reviewed-by: Romain Naour <romain.naour@gmail.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>