spi/rtc-{ds1390,ds3234,m41t94}: Use spi_get_drvdata() for SPI devices

The recently increased type checking in platform_get_drvdata() reveals a few
offenders:

drivers/rtc/rtc-ds1390.c:161: warning: passing argument 1 of ‘platform_get_drvdata’ from incompatible pointer type
drivers/rtc/rtc-ds3234.c:161: warning: passing argument 1 of ‘platform_get_drvdata’ from incompatible pointer type
drivers/rtc/rtc-m41t94.c:139: warning: passing argument 1 of ‘platform_get_drvdata’ from incompatible pointer type

Use spi_get_drvdata() instead of platform_get_drvdata().

Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>
Signed-off-by: Grant Likely <grant.likely@secretlab.ca>
diff --git a/drivers/rtc/rtc-ds3234.c b/drivers/rtc/rtc-ds3234.c
index a774ca3..bbd2622 100644
--- a/drivers/rtc/rtc-ds3234.c
+++ b/drivers/rtc/rtc-ds3234.c
@@ -158,7 +158,7 @@
 
 static int __devexit ds3234_remove(struct spi_device *spi)
 {
-	struct rtc_device *rtc = platform_get_drvdata(spi);
+	struct rtc_device *rtc = spi_get_drvdata(spi);
 
 	rtc_device_unregister(rtc);
 	return 0;