OMAP2+: Fix 9 section mismatch(es) warnings from mach-omap2/built-in.o

The serial*_data should have been marked as __initdata as per
it's usage in the board files. Fix the same to remove the
section mismatch warnings caused by it.

Signed-off-by: Santosh Shilimkar <santosh.shilimkar@ti.com>
Signed-off-by: Silesh C V <silesh@ti.com>
[tony@atomide.com: updated with additional fixes from Silesh]
Signed-off-by: Tony Lindgren <tony@atomide.com>