soc: espressif: add misssing external xtal kconfig entry

External XTAL usage is missing a Bootstrap Cycle configuration
in Kconfig, causing build to failure when CONFIG_RTC_CLK_SRC_EXT_CRYS
is selected.

Fixes #72190

Signed-off-by: Sylvio Alves <sylvio.alves@espressif.com>
4 files changed