lv_btnmatrix_set_btn_ctrl() function
Set the attributes of a button of the button matrix
Arguments
obj
pointer to button matrix object
btn_id
0 based index of the button to modify. (Not counting new lines)
ctrl
OR-ed attributs. E.g. `LV_BTNMATRIX_CTRL_NO_REPEAT | LV_BTNMATRIX_CTRL_CHECKABLE`