Fix pcspk build with kvm disabled

Fix pcspk build with kvm disabled

Errors are:

  hw/pcspk.c:85: error: expected declaration specifiers or ‘...’ before ‘kvm_pit_state’
  hw/pcspk.c:87: error: expected declaration specifiers or ‘...’ before ‘kvm_pit_state’
  hw/pcspk.c: In function ‘pcspk_callback’:
  hw/pcspk.c:114: error: too many arguments to function ‘kvm_get_pit_ch2’
  hw/pcspk.c: In function ‘pcspk_ioport_read’:
  hw/pcspk.c:161: error: too many arguments to function ‘kvm_get_pit_ch2’
  hw/pcspk.c: In function ‘pcspk_ioport_write’:
  hw/pcspk.c:171: error: storage size of ‘inkernel_state’ isn’t known
  hw/pcspk.c:175: error: too many arguments to function ‘kvm_get_pit_ch2’
  hw/pcspk.c:185: error: too many arguments to function ‘kvm_set_pit_ch2’
  hw/pcspk.c:171: warning: unused variable ‘inkernel_state’

Signed-off-by: Mark McLoughlin <markmc@redhat.com>
Cc: Jan Kiszka <jan.kiszka@web.de>