max8925_power: Do not detect ac insert if handled by other code

On brownstone rev 4 ac-insert detect is handled by vbus.

allow the platform code to configure the disabling of insert
by setting no_insert_detect.

Signed-off-by: Philip Rakity <prakity@marvell.com>
Signed-off-by: Anton Vorontsov <cbouatmailru@gmail.com>