eficonfig command reads all possible UEFI load options from 0x0000 to 0xFFFF to construct the menu. This takes too much time in some environment. This commit uses efi_get_next_variable_name_int() to read all existing UEFI load options to significantlly reduce the count of efi_get_var() call. Signed-off-by: Masahisa Kojima <masahisa.kojima@linaro.org>