MIPS: Alchemy: Add devboard machine type to cpuinfo

Prints the devboard name in cpuinfo "machine" line.

Signed-off-by: Manuel Lauss <manuel.lauss@gmail.com>
Cc: James Hogan <james.hogan@imgtec.com>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/15285/


Signed-off-by: Ralf Baechle <ralf@linux-mips.org>