[flang] Add type-specific runtime entries for Minloc/Maxloc.

We used to have a big switch statement over the type categories and kinds
inside Minloc/Maxloc. After D133051 the switch grew bigger, and this
changed inlining decisions made by GCC (the build compiler). Some of the
simple methods stopped being inlined, and this caused slight performance
regression in Polyhedron/gas_dyn2. This change adds separate entries
for real/integer data types to let them be optimized separately.

Differential Revision: https://reviews.llvm.org/D135610