soc/espressif/esp32c6: Do not set HAS_PM or HAS_POWEROFF

The source files required for this features are not present
in the tree for this SOC.
So if CONFIG_PM or CONFIG_POWEROFF are enabled, there would
be a cmake failure.

Let's just indicate these features are not supported in
kconfig.

Signed-off-by: Alberto Escolar Piedras <alberto.escolar.piedras@nordicsemi.no>