leds: pm8xxx: Enable PWM LPG banks based on max current

The current design enables PWM LPG high bank with out
checking the max current. So enable PWM LPG low bank when max
current configured as 4mA and enable PWM LPG high bank when
the max current configured as 8mA. Enabled both PWM LPG low bank
and PWM LPG high bank when max current configure as 12mA.

CRs-Fixed: 486318
Change-Id: Ib7177aafc63c4c33b8c144d665a11d5aaf0ef584
Signed-off-by: Prasad Sodagudi <psodagud@codeaurora.org>