Bluetooth: Add common Kconfig option to disable PHY Update

This adds common option to disable support for PHY Update
procedure in controller and host.
This will reduce flash usage by compiling out le_phy_update_complete
event handler that will never be called if controller has been
compiled with BT_CTLR_PHY option disabled.

Signed-off-by: Mariusz Skamra <mariusz.skamra@codecoup.pl>