[flang] fix MAXVAL(x%array_comp_with_custom_lower_bounds) (#129684)
The HLFIR inlining of MAXVAL kicks in at O1 and more when the argument
is an array component reference but the implementation did not account
for the rare cases where the array components have non default lower
bounds.
This patch fixes the issue by using `getElementAt` to compute the
element address.
Rename `indices` to `oneBasedIndices` for more clarity.