power: smb5: Dynamically adjust DCIN ICL

This patch changes the existing fixed DCIN Input Current Limit (ICL) to
instead use a ramp-up scheme that causes the ICL to reach its maximum
value gradually in steps of 100 mA from a starting value of 100 mA.

Now, every time DCIN is detected, a DCIN ICL determination will be
performed. The ICL will rise incrementally, finally settling down to the
internally-set maximum DCIN AICL value, or that value which causes the
wireless charging adaptor to hit its power limit and generate DCIN UV
interrupts in response, whichever is lesser.

DCIN AICL is also re-run every time the wireless output voltage is
reduced through the DC PSY.

Change-Id: I7c6c31958e92f16387bf4cb5de7fbf4572fcce26
Signed-off-by: Guru Das Srinagesh <gurus@codeaurora.org>