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-imx31.c b/arch/arm/mach-imx/clk-imx31.c
index 729d1a9..d9ff16e 100644
--- a/arch/arm/mach-imx/clk-imx31.c
+++ b/arch/arm/mach-imx/clk-imx31.c
@@ -124,7 +124,7 @@
 	clk_register_clkdev(clk[cspi3_gate], NULL, "imx31-cspi.2");
 	clk_register_clkdev(clk[pwm_gate], "pwm", NULL);
 	clk_register_clkdev(clk[wdog_gate], NULL, "imx2-wdt.0");
-	clk_register_clkdev(clk[rtc_gate], NULL, "mxc_rtc");
+	clk_register_clkdev(clk[rtc_gate], NULL, "imx21-rtc");
 	clk_register_clkdev(clk[epit1_gate], "epit", NULL);
 	clk_register_clkdev(clk[epit2_gate], "epit", NULL);
 	clk_register_clkdev(clk[nfc], NULL, "imx27-nand.0");