power: smb-lib: enable DPDM regulator at CC attach

In case of quick back-to-back  insertion/removal of USB
there is a possibility that VBUS does not fall below the
1V usb-plugout threshold and hence the subsequent insertion
does not generate a plug-in event. This keeps the DPDM
regulator disabled at insertion thus impacting the APSD result.

Fix this by voting to enable the DPDM regulator in the cc-attach
handler.

CRs-Fixed: 2042071
Change-Id: I37a32081f0847965e34eb1c4114602ec61e9a005
Signed-off-by: Ashay Jaiswal <ashayj@codeaurora.org>