drivers: charger: charger_max20335: rename macro to reduce ambiguity

The ILimCntl name can be understood as both register name and its field
name. Therefore it is better to change macro name so it contains both
register and field name. Second field of this register will be also
utilized by this driver in the future and new code will be aligned to
this naming convention.

Signed-off-by: Lukasz Madej <l.madej@grinn-global.com>