hwmon: (jz4740) Use devm_ioremap_resource()

Use devm_ioremap_resource() in order to make the code simpler,
and move 'struct resource *mem' from 'struct jz4740_hwmon' to
jz4740_hwmon_probe() because the 'mem' variable is used only in
jz4740_hwmon_probe(). Also the redundant return value check of
platform_get_resource() is removed, because the value is checked
by devm_ioremap_resource().

Signed-off-by: Jingoo Han <jg1.han@samsung.com>
Acked-by: Lars-Peter Clausen <lars@metafoo.de>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>