x86: Fix reference to QEMU variant of write_acpi_tables()

The commit

  eece493a7a ("cmd: qfw: bring ACPI generation code into qfw core")

moves ACPI related code to another file and missed an update of
references in acpi_table.c.

Do it now.

Fixes: eece493a7a ("cmd: qfw: bring ACPI generation code into qfw core")
Cc: Miao Yan <yanmiaobest@gmail.com>
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>

arch/x86/lib/acpi_table.c

@@ -357,8 +357,7 @@ void enter_acpi_mode(int pm1_cnt)
 }
 
 /*
- * QEMU's version of write_acpi_tables is defined in
- * arch/x86/cpu/qemu/acpi_table.c
+ * QEMU's version of write_acpi_tables is defined in drivers/misc/qfw.c
  */
 ulong write_acpi_tables(ulong start)
 {