arm: aarch64: xenvm: fix typo in Xen VM doc
arm: aarch64: xenvm: fix typo in Xen VM doc

This commit fixes hotkey for exiting Xen virtual console with correct
combination.

Signed-off-by: Dmytro Firsov <9800c905ad516cb69a0a44d48b2e9aea877d3a61@epam.com>

zephyrproject-rtos/zephyr,galak/zephyr,finikorg/zephyr,galak/zephyr,finikorg/zephyr,zephyrproject-rtos/zephyr,finikorg/zephyr,galak/zephyr,galak/zephyr,finikorg/zephyr,zephyrproject-rtos/zephyr,zephyrproject-rtos/zephyr,galak/zephyr,zephyrproject-rtos/zephyr,finikorg/zephyr