Babystep reset fix

[kisslorand]

Requirements

BTT or MKS TFT

Description

If BABYSTEP_DEFAULT_VALUE in "Configuration.h" is defined other than 0 (zero) than "Babystep reset" doesn't function as expected:

• if the babystep value is equal to BABYSTEP_DEFAULT_VALUE than babystep value remains unchanged otherwise it always resets to 0 (zero) and not to the defined babystep default value
• Z offset value will not reset to it's original value, it will have unexpected values, depending on the previous babystep value

Steps to reproduce:

• set BABYSTEP_DEFAULT_VALUE to any other value than 0 (zero) in the source code, compile and upload it to your TFT
• go to Settings -> Move -> Babystep menu
• press "Reset" repeatedly a few times and observe Z offset value
• change babystep value, press "Reset" and observe the new resulting babystep and Z offset value

This PR is meant to fix these and make "Reset babystep" to behave as expected.

Benefits

• using BABYSTEP_DEFAULT_VALUE other than 0 (zero) will not mess up the "Babystep reset" procedure

Related Issues

• none reported