boot: correct the default sequence of boot methods

The default sequence of boot methods is determined by alphabetical sorting
during linkage.

* efi_mgr must run before efi to be UEFI compliant
* pxe should run as last resort

Signed-off-by: Heinrich Schuchardt <heinrich.schuchardt@canonical.com>
Reviewed-by: Ilias Apalodimas <ilias.apalodimas@linaro.org>
4 files changed