hw/pc.c: Fix converting of ioport_register* to MemoryRegion

The commit 258711 introduced MemoryRegion to replace ioport_region*
for ioport 80h and F0h.
A MemoryRegion needs to have both read and write callback otherwise a segfault
will occur when an access is made.

The previous behaviour of this both ioport is to return 0xffffffffffffffff.
So keep this behaviour.

Reported-by: Adam Lackorzynski <adam@os.inf.tu-dresden.de>
Signed-off-by: Julien Grall <julien.grall@citrix.com>
Tested-by: Adam Lackorzynski <adam@os.inf.tu-dresden.de>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>

hw/pc.c

diff --git a/hw/pc.c b/hw/pc.c
index df0c48e..90b1bf7 100644
--- a/hw/pc.c
+++ b/hw/pc.c
@@ -103,6 +103,11 @@
 {
 }
 
+static uint64_t ioport80_read(void *opaque, hwaddr addr, unsigned size)
+{
+    return 0xffffffffffffffff;
+}
+
 /* MSDOS compatibility mode FPU exception support */
 static qemu_irq ferr_irq;
 
@@ -123,6 +128,11 @@
     qemu_irq_lower(ferr_irq);
 }
 
+static uint64_t ioportF0_read(void *opaque, hwaddr addr, unsigned size)
+{
+    return 0xffffffffffffffff;
+}
+
 /* TSC handling */
 uint64_t cpu_get_tsc(CPUX86State *env)
 {
@@ -960,6 +970,7 @@
 
 static const MemoryRegionOps ioport80_io_ops = {
     .write = ioport80_write,
+    .read = ioport80_read,
     .endianness = DEVICE_NATIVE_ENDIAN,
     .impl = {
         .min_access_size = 1,
@@ -969,6 +980,7 @@
 
 static const MemoryRegionOps ioportF0_io_ops = {
     .write = ioportF0_write,
+    .read = ioportF0_read,
     .endianness = DEVICE_NATIVE_ENDIAN,
     .impl = {
         .min_access_size = 1,