cmd: efidebug: Disable 'capsule disk-update' when CONFIG_EFI_CAPSULE_ON_DISK=n

Disable 'capsule disk-update' option for the efidebug command
when CONFIC_EFI_CAPSULE_ON_DISK is disabled, because this option
is available only when the EFI capsule update on disk is enabled.

Signed-off-by: Masami Hiramatsu <masami.hiramatsu@linaro.org>
Suggested-by: Heinrich Schuchardt <xypron.glpk@gmx.de>