#484 FDD motor on handling problem

[Gergely Szasz]

chris born reported with +D interface if "... disc two is enabled but empty. after the error message 'CHECK DISC in drive, 0:1' disc ONE will message the SAME and thus blocking access until a hard reset is made. " ([278191d7cb#c7dd])

The problem is around the FDD motor on "signal" is lost, when disk is not loaded...

[Gergely Szasz]

This patch try to correct the motor on problem of WD1770/WD1772 emulation:

Changes:

* wd_fdc.h:
    - add a new function to wd_fdc struct: fdd_motoron
* wd_fdc.c:
    * in wd_fdc_master_reset():
        *  remove pending events
        *  switch off motor on drives
    *  in wd_fdc_alloc(): set fdd_motoron function to fdd_motoron(). Later in specific drive emulation code can override if needed.
    *  replace all fdd_motoron(..) with f->fdd_motoron(...)
    *  when force interrupt command, we add a motor_off event (force interrupt start motor but never stop...?) all this we do if WD1770/1772 (other chips there is no /MO output (maybe head load?)
*  fdd.c:
*    fdd_motoron(): remove motoron "guard" if there is no disk loaded (drive motoron now independent of disk loaded status)
    *  fdd_load(): "start" rotating the disk if motor already "running"
    *  fdd_unload(): remove motoroff
*  beta.c:
    *  add beta_motoron() to override fdd_motoron() -- in beta_init() -- to start all drives motor if "head load"!
*  disciple.c:
    *  add disciple_motoron() to override fdd_motoron() -- in disciple_init() --to start all drives motor if WD /MO activated
    *  in disciple_cn_write() remove the fdd_motoron() code and change the code to do drive select, head select and dden select only if register changed
*  opus.c:
    *  add opus_motoron() to override fdd_motoron() -- in opus_init() -- to start all drives motor if  if WD /MO activated
*  plusd.c:
    *  add plusd_motoron() to override fdd_motoron() -- in plusd_init() --to start all drives motor if WD /MO activated
    *  in plusd_reset() we reset the plusd_control_register
    *  in plusd_dr_write() mask the controll register with the exists bits (4 bit B0,B1, B6, B7), and change the code to do drive select and head select only if register changed