fdc: Deprecate configuring floppies with -global isa-fdc

Deprecate

    -global isa-fdc.driveA=...
    -global isa-fdc.driveB=...

in favour of

    -device floppy,unit=0,drive=...
    -device floppy,unit=1,drive=...

Same for the other floppy controller devices.

Signed-off-by: Markus Armbruster <armbru@redhat.com>
Acked-by: John Snow <jsnow@redhat.com>
Message-Id: <20200622094227.1271650-7-armbru@redhat.com>

docs/qdev-device-use.txt

@@ -104,15 +104,10 @@ The -device argument differs in detail for each type of drive:
 
 * if=floppy
 
-  -global isa-fdc.driveA=DRIVE-ID
-  -global isa-fdc.driveB=DRIVE-ID
+  -device floppy,unit=UNIT,drive=DRIVE-ID
 
-  This is -global instead of -device, because the floppy controller is
-  created automatically, and we want to configure that one, not create
-  a second one (which isn't possible anyway).
-
-  Without any -global isa-fdc,... you get an empty driveA and no
-  driveB.  You can use -nodefaults to suppress the default driveA, see
+  Without any -device floppy,... you get an empty unit 0 and no unit
+  1.  You can use -nodefaults to suppress the default unit 0, see
   "Default Devices".
 
 * if=virtio
@@ -385,7 +380,7 @@ some DEVNAMEs:
 
     default device      suppressing DEVNAMEs
     CD-ROM              ide-cd, ide-drive, ide-hd, scsi-cd, scsi-hd
-    isa-fdc's driveA    floppy, isa-fdc
+    floppy              floppy, isa-fdc
     parallel            isa-parallel
     serial              isa-serial
     VGA                 VGA, cirrus-vga, isa-vga, isa-cirrus-vga,