Merge tag 'spi-acpi-lookup-dummy' of https://git.kernel.org/pub/scm/linux/kernel...

spi: Add empty versions of ACPI lookup functions

A patch from Richard Fitzgerald adding dummy versions of the ACPI lookup
functions for SPI:

    Provide empty versions of acpi_spi_count_resources(),
    acpi_spi_device_alloc() and acpi_spi_find_controller_by_adev()
    if the real functions are not being built.

    This commit fixes two problems with the original definitions:

    1) There wasn't an empty version of these functions
    2) The #if only depended on CONFIG_ACPI. But the functions are implemented
       in the core spi.c so CONFIG_SPI_MASTER must also be enabled for the real
       functions to exist.