ARM: palmtreo: replace #if defined with IF_ENABLED

Use IF_ENABLED macro from kconfig.h.  Thanks Sergei.

Signed-off-by: Mike Dunn <mikedunn@newsguy.com>
Acked-by: Tomas Cech <sleep_walker@suse.cz>
Signed-off-by: Haojian Zhuang <haojian.zhuang@gmail.com>