power: smb2: Handle QC2.0 charger collapse gracefully

Adaptors that are non-compliant with QC2.0 are incapable of fulfilling
either a 9V or 12V request. In such cases, when the SMB5 makes such a
request, USB input collapse occurs - leading to an under-voltage
situation and suspension of the charger buck.

Fix this by by limiting the adaptor to a lower level, 5V or 9V
correspondingly.

Change-Id: Ib0d1fc025f34f87506cb351bc9169cac42f4d61d
Signed-off-by: Harry Yang <harryy@codeaurora.org>
Signed-off-by: Guru Das Srinagesh <gurus@codeaurora.org>