rtc: max31335: use correct CONFIG symbol in IS_REACHABLE()

rtc: max31335: use correct CONFIG symbol in IS_REACHABLE()

IS_REACHABLE() is meant to be used with full symbol names from a kernel
.config file, not the shortened symbols used in Kconfig files, so
change HWMON to CONFIG_HWMON in 3 places.

Fixes: dedaf03b99d6 ("rtc: max31335: add driver support")
Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Acked-by: Nuno Sá <nuno.sa@analog.com>
Link: https://patch.msgid.link/20260108045432.2705691-1-rdunlap@infradead.org
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>