qmp: Clean up type usage in qmp_memchar_write(), qmp_memchar_read()

Const-correctness, consistently use standard C types instead of mixing
them with GLib types.

Signed-off-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
diff --git a/qemu-char.c b/qemu-char.c
index 2bdd1bb..b1c6132 100644
--- a/qemu-char.c
+++ b/qemu-char.c
@@ -2758,9 +2758,9 @@
                        Error **errp)
 {
     CharDriverState *chr;
-    guchar *write_data;
+    const uint8_t *write_data;
     int ret;
-    gsize write_count;
+    size_t write_count;
 
     chr = qemu_chr_find(device);
     if (!chr) {
@@ -2793,7 +2793,7 @@
                        Error **errp)
 {
     CharDriverState *chr;
-    guchar *read_data;
+    uint8_t *read_data;
     size_t count;
     char *data;