Bluetooth: Fix for supervision timeout must be 6X connection interval

Added a new function to verify whether the LE Connection Update
parameters are valid instaed of verifying all the LE Connection
parameters since only update parameters are set in the Connection
Update Request.

CRs-Fixed: 387146
Change-Id: I9fe6b51e44e2793f3945613fdfde3a039804746f
Signed-off-by: Archana Ramachandran <archanar@codeaurora.org>