power: qpnp-smbcharger: draw correct current requested by USB

When the USB driver specifies 0mA in the USB power supply, it actually
allows the charger driver to draw 100mA as per the unenumerated USB
specifications.

Currently the qpnp-smbcharger driver suspends the USB charge path when 0mA
is requested. This is incorrect. Only suspend the charge path when 2mA
is requested by the USB driver. Otherwise, use 100mA as the input
current limit.

Change-Id: I2a95ac096ec20c9795d579daf3ebf7c355b51769
Signed-off-by: Xiaozhe Shi <xiaozhes@codeaurora.org>