mmc: Standardize header file inclusion checks.

Standardize the checks for multiple MMC header file inclusion,
including adding comments to terminating #endif's, and fixing
one incorrect comment.

Signed-off-by: Robert P. J. Day <rpjday@crashcourse.ca>
Signed-off-by: Chris Ball <cjb@laptop.org>
diff --git a/include/linux/mmc/core.h b/include/linux/mmc/core.h
index b6718e5..791f060 100644
--- a/include/linux/mmc/core.h
+++ b/include/linux/mmc/core.h
@@ -179,4 +179,4 @@
 
 extern u32 mmc_vddrange_to_ocrmask(int vdd_min, int vdd_max);
 
-#endif
+#endif /* LINUX_MMC_CORE_H */