omap2/3/4: serial: fix coding style indentaion

No logical code change

Fix coding style indentaion as per checkpatch.pl
Fix multi-line comment style reported by Nishanth Menon

Signed-off-by: Vikram Pandita <vikram.pandita@ti.com>
Cc: Nishanth Menon <nm@ti.com>
Acked-by: Kevin Hilman <khilman@deeprootsystems.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>