EFI: add arch specific function to control use of config file

EFI: add arch specific function to control use of config file

The x86 EFI build of Xen always uses a configuration file to load modules, but
the ARM version can either use a config file to specify the modules, or be
loaded by GRUB in which case GRUB loads the modules and adds them to the DTB
that is passed to Xen.  Add the efi_arch_use_config_file() to indicate if a
configuration file is required.  For x86, this will always be true.  ARM will
examine the DTB passed via EFI configuration table (if any), and if it contains
module information will use that that not use the configuration file at all.
Add Emacs footer to efi-boot.h and boot.c

Signed-off-by: Roy Franz <roy.franz@linaro.org>
Acked-by: Jan Beulich <jbeulich@suse.com>