With upcoming changes to EDK2, allocations of type EFI_LOADER_DATA may
not return regions with execute ability. Since modules are loaded onto
the heap, change the heap allocation type to GRUB_EFI_LOADER_CODE in
order to permit execution on systems with this feature enabled.
Closes: 50420
Signed-off-by: Leif Lindholm <leif.lindholm@linaro.org>