ISSI RGB SPLIT MATRIX POC

[dexter93]

POC for split RGB on issi drivers.

This takes advantage of the existing stack, using split_count to generate 2 seperate led tables instead of 1 common one.

const is31fl3731_led_t PROGMEM g_is31fl3731_leds_left[IS31FL3731_LED_COUNT_LEFT] = {
/* Refer to IS31 manual for these locations
 *   driver
 *   |  R location
 *   |  |      G location
 *   |  |      |      B location
 *   |  |      |      | */
    {0, C1_3,  C2_3,  C3_3},
    ....
}
const is31fl3731_led_t PROGMEM g_is31fl3731_leds_right[IS31FL3731_DRIVER_COUNT_RIGHT]= {
/* Refer to IS31 manual for these locations
 *   driver
 *   |  R location
 *   |  |      G location
 *   |  |      |      B location
 *   |  |      |      | */
    {0, C1_3,  C2_3,  C3_3},
    ....
}

Allowing for individual control without being heavy on RAM/wasted cycles.

LED indexing is now treated similarly to the matrix indexing on split
[leds left]
[leds right]

but it should be transparent to the core driver.

User has to define individual driver I2C addresses for each half.

#define  IS31FL3731_I2C_ADDRESS_LEFT_1 
#define  IS31FL3731_I2C_ADDRESS_LEFT_2
..
#define IS31FL3731_I2C_ADDRESS_RIGHT_1
#define IS31FL3731_I2C_ADDRESS_RIGHT_2
..

and define the size of each

#define RGB_MATRIX_SPLIT 34 65

This is a POC, suggestions most welcome.

Description

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

Checklist

• My code follows the code style of this project: C, Python
• I have read the PR Checklist document and have made the appropriate changes.
• 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).