[M] Change in coreboot[master]: cbmem_top: Change the return value to uintptr_t

[Elyes Haouas (Code Review)]

Attention is currently required from: Raul Rangel, Jeff Daly, Jakub Czapiga, Jonathan Zhang, Matt DeVillier, Julius Werner, Angel Pons, Arthur Heymans, Andrey Petrov, Lance Zhao, Jason Glenesk, Johnny Lin, Tim Wawrzynczak, Christian Walter, Vanessa Eusebio, Fred Reitberger, Felix Held, Tim Chu.

Elyes Haouas has posted comments on this change. ( https://review.coreboot.org/c/coreboot/+/69163 )

Change subject: cbmem_top: Change the return value to uintptr_t
......................................................................

Patch Set 9:

This change is ready for review.