rtc: isl1208: Fix incorrect logic in isl1208_set_xtoscb()

rtc: isl1208: Fix incorrect logic in isl1208_set_xtoscb()

The XTOSCB bit is not bit 0, but xtosb_val is either 0 or 1. If it is 1,
test will never succeed. Fix this issue by using double negation.

While at it, remove unnecessary blank line from probe().

Reported-by: Pavel Machek <pavel@denx.de>
Closes: https://lore.kernel.org/all/ZN4BgzG2xmzOzdFZ@duo.ucw.cz/
Signed-off-by: Biju Das <biju.das.jz@bp.renesas.com>
Reviewed-by: Pavel Machek <pavel@denx.de>
Link: https://lore.kernel.org/r/20230817161038.407960-1-biju.das.jz@bp.renesas.com
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>