[Linaro-acpi] [PATCHv3] grub armacpi implementation

Hi, this is v3 of the patch after review from Leif. Leif it would be good if you could carry this in your branch to save us having to maintain another grub tree.

Changes since v2: Updates to pointer types to prevent compile warnings (-Werror issues) from Leif

Changes since v1: Address Leifs comments:- return type for grub_cmd_armcpi does not return with bogus error leaving file open, not jumps to out: properly bogus whitespace change removed.

Thanks

Graeme