grub-efi.bbclass: Add serial and graphics menu options
The syslinux.bbclass already has support for automatically generated
serial and graphics menu choices. This patch adds the same concept to
the grub-efi menu. That makes it possible to generate a single image
which can boot on a PCBIOS or EFI firmware with consistent looking
boot options.
[YOCTO #4100]
Signed-off-by: Jason Wessel <jason.wessel@windriver.com> Signed-off-by: Saul Wold <sgw@linux.intel.com> Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
