gummiboot: Remove/change gummiboot references with systemd-boot
After systemd-boot was introduced, its been tested for a while with no major
issues being found until now, this patch completely replaces all gummiboot
instances with systemd-boot ones, taking the next step into cleaning
up systemd-boot/gummiboot.
[YOCTO #10332]
Signed-off-by: Alejandro Hernandez <alejandro.hernandez@linux.intel.com> Signed-off-by: Ross Burton <ross.burton@intel.com>
