soundwire: bus: use FIELD_GET()

use FIELD_GET() in bus code to extract field values instead of open
coding masks and shift operations.

Signed-off-by: Vinod Koul <vkoul@kernel.org>
Tested-by: Bard Liao <yung-chuan.liao@linux.intel.com>
Link: https://lore.kernel.org/r/20200903114504.1202143-3-vkoul@kernel.org


Signed-off-by: Vinod Koul <vkoul@kernel.org>