dmaengine: PL08x: Avoid collisions with get_signal() macro

As pointed out by Arnd Bergmann there is a get_signal macro definied in
linux/signal.h which can conflict with the platform data callback
function of the same name leading to confusing errors from the compiler
(especially if signal.h manages to get pulled into the driver itself due
to header dependencies).  Avoid such errors by renaming get_signal and
put_signal in the platform data to get_xfer_signal and put_xfer_signal.

Signed-off-by: Mark Brown <broonie@linaro.org>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Vinod Koul <vinod.koul@intel.com>