efi_loader: out of resources in AllocatePages()

According to the UEFI AllocatePages() has to return EFI_OUT_OF_RESOURCES if
sufficient memory is not available.

Change the return value.

UEFI SCT II (2017): 3.2.1 AllocatePages(), 5.1.2.1.8

Signed-off-by: Heinrich Schuchardt <xypron.glpk@gmx.de>