[flang][acc] remap variable in device_ptr clauses (#177018)
I previously disabled the variable remapping to data operand results in
the IR for the deviceptr clause because it was not clear how fir.box
would be dealt with and the remapping increased the usage of fir.box.
Since then, it was clarified that lowering could use fir.box and that it
would be up to the runtime to deal with the fact that the fir.box is
implemented by a descriptor allocated on the host and containing the
base address of an entity on the device.
Remove the workaround.