Input: xpad - fix some coding style issues

[ Upstream commit 68c78d0155e37992268664e134996d2b140ddf38 ]

Fix some coding style issues reported by checkpatch.pl. Mostly brackets
in macros, spacing and comment style.

Signed-off-by: Leo Sperling <leosperling97@gmail.com>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>