power: ipaq-micro-battery: use __maybe_unused to hide pm functions

power: ipaq-micro-battery: use __maybe_unused to hide pm functions

The ipaq micro battery driver has suspend/resume functions that
are accessed using SIMPLE_DEV_PM_OPS, which hide the reference
when CONFIG_PM_SLEEP is not set, resulting in a warning about
unused functions:

drivers/power/ipaq_micro_battery.c:284:12: error: 'micro_batt_suspend' defined but not used [-Werror=unused-function]
drivers/power/ipaq_micro_battery.c:292:12: error: 'micro_batt_resume' defined but not used [-Werror=unused-function]

This adds __maybe_unused annotations to let the compiler know
it can silently drop the function definition.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Sebastian Reichel <sre@kernel.org>