Platform/RPi/AcpiTables: Move PPTT constants to the alsc source

There's no real reason to have the PPTT constants factorized in
AcpiTables.h, and hiding them away with the interrupts is only
going to end up being counter-productive for folks trying to
understand or maintain the code.

Move these sections to Pptt.aslc where they belong.

Signed-off-by: Pete Batard <pete@akeo.ie>
Reviewed-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>