rtc: ab8500: replace sprintf() with sysfs_emit()

rtc: ab8500: replace sprintf() with sysfs_emit()

This patch replaces sprintf() with sysfs_emit() to ensure proper
bounds checking. It also simplifies the return logic by directly
returning the error after logging, instead of logging, calling
sprintf(), then returning.

Reviewed-by: Linus Walleij <linusw@kernel.org>
Signed-off-by: Maxwell Doose <m32285159@gmail.com>
Link: https://patch.msgid.link/20260503201236.29685-1-m32285159@gmail.com
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>