Fix sections for omap-mcbsp platform driver

Don't use __init but __devinit to define probe function.  A pointer to
omap_mcbsp_probe is passed to the core via platform_driver_register and
so the function must not disappear when the init code is freed.  Using
__init and having HOTPLUG=y the following probably oopses:

	echo -n omap-mcbsp.1 > /sys/bus/platform/driver/omap-mcbsp/unbind
	echo -n omap-mcbsp.1 > /sys/bus/platform/driver/omap-mcbsp/bind

While at it move the remove function to the .devexit.text section.

Signed-off-by: Uwe Kleine-König <ukleinek@strlen.de>
Cc: Russell King <rmk+kernel@arm.linux.org.uk>
Signed-off-by: Tony Lindgren <tony@atomide.com>