drivers/leds/leds-tca6507.c: cleanup error handling in tca6507_probe()

Just a small tidy-up.

1) There is a NULL dereference if the tca allocation fails.
2) The call to cancel_work_sync() isn't needed because we haven't
   scheduled any work.
3) The call to i2c_set_clientdata() isn't needed because the core
   handles that automatically if probe() fails.
4) I added some curly braces for style reasons.

Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Cc: Richard Purdie <rpurdie@rpsys.net>
Acked-by: NeilBrown <neilb@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>