loader: extract rom_free() function

The next patch will need to free a rom.  There is already code to do
this in rom_add_file().

Note that rom_add_file() uses:

  rom = g_malloc0(sizeof(*rom));
  ...
  if (rom->fw_dir) {
      g_free(rom->fw_dir);
      g_free(rom->fw_file);
  }

The conditional is unnecessary since g_free(NULL) is a no-op.

Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Alistair Francis <alistair.francis@wdc.com>
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Message-id: 20180814162739.11814-4-stefanha@redhat.com
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

hw/core/loader.c

@@ -847,6 +847,17 @@ struct Rom {
 static FWCfgState *fw_cfg;
 static QTAILQ_HEAD(, Rom) roms = QTAILQ_HEAD_INITIALIZER(roms);
 
+/* rom->data must be heap-allocated (do not use with rom_add_elf_program()) */
+static void rom_free(Rom *rom)
+{
+    g_free(rom->data);
+    g_free(rom->path);
+    g_free(rom->name);
+    g_free(rom->fw_dir);
+    g_free(rom->fw_file);
+    g_free(rom);
+}
+
 static inline bool rom_order_compare(Rom *rom, Rom *item)
 {
     return ((uintptr_t)(void *)rom->as > (uintptr_t)(void *)item->as) ||
@@ -995,15 +1006,7 @@ err:
     if (fd != -1)
         close(fd);
 
-    g_free(rom->data);
-    g_free(rom->path);
-    g_free(rom->name);
-    if (fw_dir) {
-        g_free(rom->fw_dir);
-        g_free(rom->fw_file);
-    }
-    g_free(rom);
-
+    rom_free(rom);
     return -1;
 }