@Dietmar
You must use the compiled AML binary file and not the DSL file, do not rename DSL file, compile it into AML.
I may have gotten the command slightly wrong
instead of
grub> acpi (hd0,2)/acpi/dsdt.aml
it should be
grub> acpi (hd0,msdos2)/acpi/dsdt.aml
you can check if this is correct by typing
grub> acpi (hd0,msdos2)/
and then pressing TAB to see the directory listing and see where you are.
Make sure the /acpi/ folder exists.