ASoC: Intel: avs: Update AVS_FW_INIT_TIMEOUT_US declaration

To reduce the number of places to update if timeouts would have to
change, modify the constant declaration.

Signed-off-by: Cezary Rojewski <cezary.rojewski@intel.com>
Link: https://lore.kernel.org/r/20220707124153.1858249-13-cezary.rojewski@intel.com
Signed-off-by: Mark Brown <broonie@kernel.org>