Fix accsessing "PresentModifierLocs" array beyond its end. (#73579)

Currently PresentModifierLocs defined with size DefaultmapKindNum; where
DefaultmapKindNum = OMPC_DEFAULTMAP_pointer + 1

Before 5.0 variable-category can not be omitted. For the test like
\#pragma omp target map(tofrom: errors) defaultmap(present)

error would be mitted.

After 5.0 that is allowd.

When try to:
PresentModifierLocs[DMC->getDefaultmapKind()] =
              DMC->getDefaultmapModifierLoc();
It is accessed beyond array end.

To fix this using OMPC_DEFAULTMAP_unknow instead OMPC_DEFAULTMAP_poiner.