ARM: OMAP: rx51: Fix a section mismatch warn

rx51_si4713_dev is referenced only from rx51_init_si4713.
So the memory for rx51_si4713_dev can be safely freed after init.
Also it references rx51_si4713_board_info which is __initdata_or_module.

fixes the below warning.

WARNING: vmlinux.o(.data+0x30958): Section mismatch in reference from the variable rx51_si4713_dev to the (unknown reference) .init.data:(unknown)
The variable rx51_si4713_dev references
the (unknown reference) __initdata (unknown)
If the reference is valid then annotate the
variable with __init* or __refdata (see linux/init.h) or name the variable:
*_template, *_timer, *_sht, *_ops, *_probe, *_probe_one, *_console

Reported-by: Wolfram Sang <w.sang@pengutronix.de>
Signed-off-by: Shubhrajyoti D <shubhrajyoti@ti.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>