macosx: Use correct double type for a and b pos variables

Fixes the following compile warning

/Users/claucambra/Downloads/GitRepos/vlc/extras/package/macosx/../../../modules/gui/macosx/playqueue/VLCPlayerController.m:1592:85: warning: incompatible pointer types passing 'float *' to parameter of type 'double *' [-Wincompatible-pointer-types]
 1592 |     const enum vlc_player_abloop state = vlc_player_GetAtoBLoop(_p_player, &a_time, &a_pos, &b_time, &b_pos);
      |                                                                                     ^~~~~~
/Users/claucambra/Downloads/GitRepos/vlc/extras/package/macosx/../../../include/vlc_player.h:790:74: note: passing argument to parameter 'a_pos' here
  790 | vlc_player_GetAtoBLoop(vlc_player_t *player, vlc_tick_t *a_time, double *a_pos,
      |                                                                          ^
/Users/claucambra/Downloads/GitRepos/vlc/extras/package/macosx/../../../modules/gui/macosx/playqueue/VLCPlayerController.m:1592:102: warning: incompatible pointer types passing 'float *' to parameter of type 'double *' [-Wincompatible-pointer-types]
 1592 |     const enum vlc_player_abloop state = vlc_player_GetAtoBLoop(_p_player, &a_time, &a_pos, &b_time, &b_pos);
      |                                                                                                      ^~~~~~
/Users/claucambra/Downloads/GitRepos/vlc/extras/package/macosx/../../../include/vlc_player.h:791:52: note: passing argument to parameter 'b_pos' here
  791 |                        vlc_tick_t *b_time, double *b_pos);

Signed-off-by: Claudio Cambra developer@claudiocambra.com