grub-efi recipe added 'grub-efi-' prefix to the file name of
efi binary. Changed grub-efi.bbclass accordingly.
(From OE-Core rev: 860c44435ea7cbbe3517d5ab9146213cc80fd0e7)
Signed-off-by: Ed Bartosh <ed.bartosh@linux.intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>