[OpenMP] Fix incorrect diagnostics in map clause

Having the following code pattern will result in incorrect diagnostic

int main() {
  int arr[10];
#pragma omp target data map(arr[:])
#pragma omp target map(arr)
  {}
}

t.cpp:4:24: error: original storage of expression in data environment is shared
      but data environment do not fully contain mapped expression storage
#pragma omp target map(arr)
                       ^~~
t.cpp:3:29: note: used here
#pragma omp target data map(arr[:])
                            ^~~~~~
1 error generated.


Patch by David S.

Differential Revision: https://reviews.llvm.org/D22075

llvm-svn: 275926