ARM: OMAP: mcbsp: Fix possible memory corruption

Commits 09d28d ("ARM: OMAP: mcbsp: Start generalize omap2_mcbsp_set_clks_src")
and 7bc0c4 ("ARM: OMAP: mcbsp: Start generalize signal muxing functions")
incorrectly set two struct omap_mcbsp_platform_data fields after
omap_device_build_ss and kfree calls.

Fix this by moving these pdata assignments before those calls.

Signed-off-by: Jarkko Nikula <jarkko.nikula@bitmer.com>
Reported-by: NeilBrown <neilb@suse.de>
Signed-off-by: Tony Lindgren <tony@atomide.com>