[WATCHDOG] remove ARM26 sections

Removes ARM26 sections from Kconfig and Makefile, because
ARM26 is long gone.

Signed-off-by: Paulius Zaleckas <paulius.zaleckas@teltonika.lt>
Acked-by: Russell King <rmk+kernel@arm.linux.org.uk>
Signed-off-by: Wim Van Sebroeck <wim@iguana.be>