[Flang][OpenMP]Missing convert to lhsType in atomic write (#92346)

Fixes test.f90 in #83144.

This issue is observed only when a boolean constant is assigned to a
logical variable. In non-openmp flow, a conversion op is inserted before
assigning it to a logical variable. This patch will insert a fir.convert
operation when the types are not the same, before generating the atomic
write operation.

I've proposed another patch(#85059 ) which removes checks at MLIR level
and looks like it's too permissive. I'm planning to abandon this patch
and address it here.