intel: Explicitly set x86 compat in intel_ish5 and lakemont

Those dtsi are a base for a range of 32-bit platforms. Setting this
compatible makes it easier to distinguish all 32-bit x86 platforms.

Signed-off-by: Piotr Zierhoffer <pzierhoffer@antmicro.com>
Signed-off-by: Mateusz Hołenko <mholenko@antmicro.com>

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