Update is31fl3731-simple

[Xelus22]

Update the current IS31FL3731-simple.c to reflect changes for more than 1 driver.
This is a draft as @drashna has advised as this is my first proper helpful PR.
Please critique anything that is wrong.
and tag @skullydazed 😄

Description

Changes code to reflect the number of drivers to update.

Update g_led_control_registers_update_required to false since it does not in the original code.

Types of Changes

• Core
• Bugfix
• New feature
• Enhancement/optimization
• Keyboard (addition or update)
• Keymap/layout/userspace (addition or update)
• Documentation

Issues Fixed or Closed by This PR

• Use of more than 1 is31fl3731 driver when using the simple driver

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.
• I have tested the changes and verified that they work and don't break anything (as well as I can manage).

[stale]

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