Remove reduntant qemu: from error functions

This patch removes redundant "qemu:" from error functions. The link to the bitesized task is:
http://wiki.qemu-project.org/Contribute/BiteSizedTasks#Error_checking

Signed-off-by: Ishani Chugh <chugh.ishani@research.iiit.ac.in>
Reviewed-by: Eduardo Habkost <ehabkost@redhat.com>
Reviewed-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>

hw/nios2/boot.c

@@ -197,7 +197,7 @@ void nios2_load_kernel(Nios2CPU *cpu, hwaddr ddr_base,
                                                   ram_size - initrd_offset);
             }
             if (initrd_size < 0) {
-                error_report("qemu: could not load initrd '%s'",
+                error_report("could not load initrd '%s'",
                              initrd_filename);
                 exit(EXIT_FAILURE);
             }