util/ifdtool: add generic `PLATFORM_IFD2` for early SoC development

util/ifdtool: add generic `PLATFORM_IFD2` for early SoC development

`PLATFORM_IFD2` macro is more generic tag that can be associated with
early next SoC platform development which using IFDv2.

The current assumption is that newer SoC platform still uses the same
SPI/eSPI frequency definition being used for latest platform(TGL, ADL)
and if the frequency definition is updated later, `PLATFORM_IFD2' will
use latest frequency definition for early next SoC development.
And once upstream is allowed for new platform, platform name will be
added in tool later.

Signed-off-by: Wonkyu Kim <wonkyu.kim@intel.com>
Change-Id: I14a71a58c7d51b9c8b92e013b5637c6b35005f22
Reviewed-on: https://review.coreboot.org/c/coreboot/+/61576
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Subrata Banik <subratabanik@google.com>