[flang] Disallow scalar argument to SIZE/LBOUND/UBOUND

The compiler accepts arguments of any rank, or assumed rank, to a host
of intrinsic inquiry functions.  For scalars, this is correct for most
of them, but the standard (and other compilers) prohibit scalar arguments
to SIZE, LBOUND, and UBOUND (without DIM=).

There are meaningful interpretations for these intrinsic inquiries
on scalars, but since there's no portability concern here, continuing
to support them would be an unjustifiable extension.

Differential Revision: https://reviews.llvm.org/D146587