tune-corei7.inc: tell qemu to emulate a matching processor

tune-corei7.inc: tell qemu to emulate a matching processor

If tune-corei7 is in use then the target binaries may contain instructions that
qemu-x86-64 can't execute by default, resulting in errors on rootfs construction:

NOTE: Running intercept scripts:
NOTE: > Executing update_font_cache intercept ...
qemu: uncaught target signal 4 (Illegal instruction) - core dumped

In this case the instruction is popcnt, part of SSE4.2, so tell Qemu to emulate
the CPU that the tune targets (in this case, Nehalem). Also pass check=false as
the Nehalem machine supports VME but user-space qemu doesn't, which produces a
warning unless CPUID checking is disabled.

[ YOCTO #8888 ]

Signed-off-by: Ross Burton <ross.burton@intel.com>