power: regulator: tps65941: Added macros for BUCK ID

Adds macros for buck and ldo ids and switched to using switch
case instead of if else in probe functions. Helps in adding
support for TPS65224 PMIC.

Signed-off-by: Bhargav Raviprakash <bhargav.r@ltts.com>
Reviewed-by: Dhruva Gole <d-gole@ti.com>
Reviewed-by: Jaehoon Chung <jh80.chung@samsung.com>