Update k3-j721e-bone-pins.h

Minor changes for gpio macros to make everything streamline.

Most of the pin macros for which two ball connections are available, one pin macro (gpio_P9_20A/B) is used to create a generic pin macro (gpio_P9_20) using the A/B macro itself like

...
#define gpio_P9_20A &main_gpio1 2
#define gpio_P9_20B &main_gpio0 77
#define gpio_P9_20 gpio_P9_20B
...

But, for some of them, the gpio number was used, and this PR fixes that issue.

...
#define gpio_P9_24A &main_gpio0 119
#define gpio_P9_24B &main_gpio0 13
#define gpio_P9_24 &main_gpio0 13
...