x86: Fix reference to QEMU variant of write_acpi_tables()

The commit

  eece493a ("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: eece493a ("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>