rtc: at91sam9: replace devm_ioremap by devm_ioremap_resource

Replace devm_ioremap calls by devm_ioremap_resource which already check
resource consistency (resource != NULL) and print an error in case of
failure.

Signed-off-by: Boris BREZILLON <boris.brezillon@free-electrons.com>
Acked-by: Alexandre Belloni <alexandre.belloni@free-electrons.com>
Acked-by: Johan Hovold <johan@kernel.org>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Nicolas Ferre <nicolas.ferre@atmel.com>