iio: qcom-spmi-adc5: update scaling ratios for SMB_ICHG and SMB_IIN

Update scaling ratios for SMB_ICHG and SMB_IIN ADC channels, following
HW recommendation. Update default prescaling values used for SMB_IIN
and ICHG_FB channels to match changes made in the prescaling array.

Change-Id: I2b016e021d3c9e8b76cd5400c6790030da088093
Signed-off-by: Jishnu Prakash <jprakash@codeaurora.org>