Fix time accuracy

[AdrianSoundy]

Description

Time was only accurate to 1millisec although time from RTC should have been accurate to 1 micro sec.
This was caused by using HAL_Time_ToSystemTime which only works down to millisecs.

Now bypass HAL_Time_ToSystemTime & HAL_Time_ConvertFromSystemTime unless date only.
This also improves performance of getting time.

Motivation and Context

Want look at passing time to gpio events so the time between events can be calculated down to 1 micro secs. This is for devices like the DHT11 & DHT22 sensors.

Types of changes

• Improvement (non-breaking change that improves a feature, code or algorithm)
• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have read the CONTRIBUTING document.
• I have added tests to cover my changes.
• All new and existing tests passed.

Signed-off-by: adriansoundy adriansoundy@gmail.com

[nfbot]

Hi @AdrianSoundy,

I'm nanoFramework bot.
Thank you for your contribution!

A human will be reviewing it shortly. 😉

[josesimoes]

LGTM