corei7 offers a significant advancement since the previous core2
cpu-type described in the tune-core2 file.

From the GCC(1):
Intel Core i7 CPU with 64-bit extensions, MMX, SSE, SSE2, SSE3,
               SSSE3, SSE4.1 and SSE4.2 instruction set support.

This offers optimizations for Nehalem and Silvermont (e.g. Bay Trail)
CPUs (and beyond).

Signed-off-by: Darren Hart <dvhart@linux.intel.com>
Cc: Richard Purdie <richard.purdie@linuxfoundation.org>
Cc: Paul Eggleton <paul.eggleton@intel.com>
Cc: Tom Zanussi <tom.zanussi@intel.com>
Cc: Nitin Kamble <nitin.a.kamble@intel.com>
Cc: Mark Hatle <mark.hatle@windriver.com>
Cc: Bruce Ashfield <bruce.ashfield@windriver.com>
Cc: Martin Jansa <martin.jansa@gmail.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>