soundwire: wrap macro argument in parenthesis

macro argument should be inside a parenthesis to avoid precedence
issues

checkpatch complains:
CHECK: Macro argument 'n' may be better as '(n)' to avoid
precedence issues

Signed-off-by: Vinod Koul <vkoul@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>