power: smb-lib: Fix sink/source insertion/removal function ordering

On PM660 the charger buck/boost frequency is configured in
the same register. Present ordering of the sink/source
removal function call causes incorrect charger frequency
configuration.

Fix this by first calling sink_removal and then source_insertion
function. Also, configure the buck frequency to the initial
5V USB value during source insertion.

Change-Id: I0d436f7e0843f2ddaa3d09db05cec403d03b6893
Signed-off-by: Anirudh Ghayal <aghayal@codeaurora.org>