[media] wl128x: use swap() in fm_rdsparse_swapbytes()

Use kernel.h macro definition.

Thanks to Julia Lawall for Coccinelle scripting support.

Signed-off-by: Fabian Frederick <fabf@skynet.be>
Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>