docs: migration_guide_4_1: migration guide entry for renamed properties

add migration guide for following renamed variables
 - ``en_spreadcycle`` to ``en-spreadcycle``
- ``i_scale_analog`` to ``i-scale-analog``
- ``index_optw``to ``index-otpw```
- ``ìndex_step`` to ``index-step``
- ``internal_rsense`` to ``internal-rsense``
- ``lock_gconf`` to ``lock-gconf``
- ``mstep_reg_select`` to ``mstep-reg-select``
- ``pdn_disable`` to ``pdn-disable``
- ``poscmp_enable`` to ``poscmp-enable``
- ``test_mode`` to ``test-mode``

Signed-off-by: Jilay Pandya <jilay.pandya@outlook.com>