When helix/rev2 was using split_common, it didn't work properly and I couldn't type on the right hand side.
The cause is that the following code, added in 0.16.0 to `quantum/keyboard.c`, does not include `quantum/split_common/split_util.h` but instead includes `keyboards/helix/rev2/split_util.h`. Therefore, `split_pre_init()/split_post_init()` in `quantum/split_common/split_util.c` was not called.
```c
#ifdef SPLIT_KEYBOARD
# include "split_util.h"
#endif
```
* is_master, has_usb() move to rev2.[hc]
* Do recent helix/rev2 changes to helix/pico as well.
helix/pico/matrix.c: remove 'is_master'
helix/pico/pico.c: add 'is_master'
helix/pico/pico.h: add 'has_usb()' macro
helix/pico/split_util.c: remove 'setup_handedness()' 'has_usb()', add 'is_helix_master()' etc
* add HELIX=scan option into {rev2/pico}/local_features.mk
Made DEBUG_MATRIX_SCAN_RATE easy to use.
* Changed rules.mk to link "helix/local_drivers/ssd1306.c" only when OLED_ENABLE = yes.
* Added option to use split_common for helix/rev2, helix/pico keyboard.
how to build:
### build helix/pico (HelixPico) with helix current codes
$ make helix/pico:KEY_MAP
$ make helix/pico/back:KEY_MAP
### build helix/rev2 (Helix or Helix beta) with helix current codes
$ make helix:KEY_MAP
$ make helix/rev2/back:KEY_MAP
$ make helix/rev2/under:KEY_MAP
$ make helix/rev2/oled:KEY_MAP
$ make helix/rev2/oled/back:KEY_MAP
$ make helix/rev2/oled/under:KEY_MAP
### build helix/pico (HelixPico) with split_common codes
$ make helix/pico/sc:KEY_MAP
$ make helix/pico/sc/back:KEY_MAP
$ make helix/pico/sc/under:KEY_MAP
### build helix/rev2 (Helix) with split_common codes
$ make helix/rev2/sc:KEY_MAP
$ make helix/rev2/sc/back:KEY_MAP
$ make helix/rev2/sc/under:KEY_MAP
$ make helix/rev2/sc/oled:KEY_MAP
$ make helix/rev2/sc/oledback:KEY_MAP
$ make helix/rev2/sc/oledunder:KEY_MAP
* add matrix_slave_scan_user() to helix/rev2/rev2.c, helix/pico/pico.h
* Changed 'helix:xulkal' to always use split_common and removed ad hoc code.
Added the following line to 'helix/rev2/keymaps/xulkal/rules.mk':
SPLIT_KEYBOARD = yes
Removed the following ad hoc code from 'users/xulkal/custom_oled.c':
#if KEYBOARD_helix_rev2
extern uint8_t is_master;
bool is_keyboard_master(void) { return is_master; }
#endif
* add '#define DIODE_DIRECTION COL2ROW' into helix/{rev2|pico}/config.h
This commit does not change the build result.
* update helix readme
* keyboards/helix/readme.md
* keyboards/helix/pico/keymaps/default/readme.md
* keyboards/helix/rev2/keymaps/default/readme.md
Co-authored-by: mtei <2170248+mtei@users.noreply.github.com>
