ite/it8xxx2: Fix JTAG support when using a flash offset

If a board defined CONFIG_FLASH_LOAD_OFFSET to a non-zero value,
enabling CONFIG_SOC_IT8XXX2_JTAG_DEBUG_INTERFACE generated a linker
error because when trying to move the location counter backwards.

Fixed by allocating the JTAG section within the deined ROM region.

Signed-off-by: Keith Short <keithshort@google.com>