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: I6686ed85d78fa55f08491a47c10581407e0cd70e
Signed-off-by: Prasad Sodagudi <psodagud@codeaurora.org>
Signed-off-by: Sridhar Gujje <sgujje@codeaurora.org>