serial: 8250: Add an empty line and remove some useless {}

This fixes the following checkpatch.pl warnings:
   WARNING: Missing a blank line after declarations
   WARNING: braces {} are not necessary for any arm of this statement

Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
Link: https://lore.kernel.org/r/257ffd691b4a062ad017333c9430d69da6dbd29a.1619594713.git.christophe.jaillet@wanadoo.fr


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>