gpu: vivante: Removed leftover VG code
gpu: vivante: Eliminated type gctSIZE_T_PTR

There was only one user; the other function that claimed to use it had
faulty documentation.
gpu: vivante: Replaced gctSIZE_T by size_t

gctSIZE_T was defined as unsigned long, but size_t seems a better fit
for the values it is used for.
gpu: vivante: Replaced gcmSIZEOF by sizeof
gpu: vivante: Eliminated gctCHAR, gctSTRING and gctCONST_STRING

Replaced them by their definitions.
gpu: vivante: Eliminated gctPOINTER and gctCONST_POINTER

Replaced them by their definitions.
gpu: vivante: Eliminated gct(U)INT* types

Replaced them by the equivalent Linux types.