power: smb135x-charger: handle usb removal in src_detect_handler only

Currently USB removal for DCP is handled in the UV interrupt
handler and SDP/CDP is handled in the source detect interrupt
handler.

Refactor the code to handle all USB removals from the source
detect interrupt handler.

Change-Id: I78124bcd44101976603214007b7673a79aeb1a53
Signed-off-by: Nicholas Troast <ntroast@codeaurora.org>