rtc: mxc_rtc: remove cpu_is_xxx by using platform_device_id

It changes the driver to use platform_device_id rather than cpu_is_xxx
to determine the controller type, and updates the platform code
accordingly.

As the result, mach/hardware.h inclusion gets removed from the driver.

Signed-off-by: Shawn Guo <shawn.guo@linaro.org>
Acked-by: Sascha Hauer <s.hauer@pengutronix.de>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: rtc-linux@googlegroups.com
diff --git a/arch/arm/mach-imx/clk-imx27.c b/arch/arm/mach-imx/clk-imx27.c
index 100e38c..86a0c42 100644
--- a/arch/arm/mach-imx/clk-imx27.c
+++ b/arch/arm/mach-imx/clk-imx27.c
@@ -259,7 +259,7 @@
 	clk_register_clkdev(clk[gpio_ipg_gate], "gpio", NULL);
 	clk_register_clkdev(clk[brom_ahb_gate], "brom", NULL);
 	clk_register_clkdev(clk[ata_ahb_gate], "ata", NULL);
-	clk_register_clkdev(clk[rtc_ipg_gate], NULL, "mxc_rtc");
+	clk_register_clkdev(clk[rtc_ipg_gate], NULL, "imx21-rtc");
 	clk_register_clkdev(clk[scc_ipg_gate], "scc", NULL);
 	clk_register_clkdev(clk[cpu_div], "cpu", NULL);
 	clk_register_clkdev(clk[emi_ahb_gate], "emi_ahb" , NULL);