ENGR00218807 ESAI: fix bootup issue cause by accessing unexist address

ENGR00218807 ESAI: fix bootup issue cause by accessing unexist address

To support p2p playback, ESAI driver would copy platform data to
esai_asrc struct. The platform data only exist on boards that supports
ESAI. However, for ARM2 board, it supports ESAI but not necessary
get the codec CS42888. Thus the probe() in ESAI driver would also try to
copy the platform data from board init file.

The p2p playback now only support ARD board, so the ESAI probe() for
ARM2 would access unexisted address and cause an kernel dump.

In the patch, check the platform data address before copy.

Signed-off-by: Chen Liangjun <b36089@freescale.com>