ucsi_ccg: Don't show non-functional attributes

ucsi_ccg: Don't show non-functional attributes

If no fw_build is recognized for the controller there is no point to
exposing the `do_flash` attribute.

Add an is_visible callback to the attribute group and check for that
fw_build member to hide when not applicable.

Signed-off-by: Mario Limonciello <mario.limonciello@amd.com>
Reviewed-by: Heikki Krogerus <heikki.krogerus@linux.intel.com>
Link: https://lore.kernel.org/r/20250221054137.1631765-3-superm1@kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>