Compile pckbd only once

Use a qemu_irq to indicate A20 line changes. Move I/O port 92
to pckbd.c.

Signed-off-by: Blue Swirl <blauwirbel@gmail.com>
diff --git a/default-configs/sparc64-softmmu.mak b/default-configs/sparc64-softmmu.mak
index 514d334..1cc3f13 100644
--- a/default-configs/sparc64-softmmu.mak
+++ b/default-configs/sparc64-softmmu.mak
@@ -6,6 +6,7 @@
 CONFIG_VGA_PCI=y
 CONFIG_SERIAL=y
 CONFIG_PARALLEL=y
+CONFIG_PCKBD=y
 CONFIG_FDC=y
 CONFIG_IDE_CORE=y
 CONFIG_IDE_QDEV=y