deps: fix v8 armv6 run-time detection

The elf_platform suffix in /proc/cpuinfo moved to the model name field
in Linux 3.8.

Out-of-tree patch pending https://codereview.chromium.org/867713003/

Fixes: https://github.com/iojs/io.js/issues/283
PR-URL: https://github.com/iojs/io.js/pull/559


Reviewed-By: Fedor Indutny <fedor@indutny.com>