ASoC: SOF: Kconfig: Make IPC_MESSAGE_INJECTOR depend on SND_SOC_SOF

Make sure that the IPC_MESSAGE_INJECTOR client can not be built in when
SND_SOC_SOF is built as module.

Fixes: cac0b088 ("ASoC: SOF: Convert the generic IPC message injector into SOF client")
Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Peter Ujfalusi <peter.ujfalusi@linux.intel.com>
Reviewed-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Link: https://lore.kernel.org/r/20220823121554.4255-3-peter.ujfalusi@linux.intel.com


Signed-off-by: Mark Brown <broonie@kernel.org>