Staging / quickstart: remove reduplicate if(acpi_disabled) check

In acpi_bus_register_driver(), there is an if (acpi_disabled) check,
so the if(acpi_disabled) before it is reduplicate, remove it.

Signed-off-by: Hanjun Guo <hanjun.guo@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>