common: cosmetic: CONFIG_BOOTFILE checkpatch compliance

Remove MK_STR from places that consume CONFIG_BOOTFILE to force all definitions to be string literals.

Signed-off-by: Joe Hershberger <joe.hershberger@ni.com>
Cc: Joe Hershberger <joe.hershberger@gmail.com>
Cc: Wolfgang Denk <wd@denx.de>
Acked-by: Mike Frysinger <vapier@gentoo.org>
diff --git a/include/configs/MPC8544DS.h b/include/configs/MPC8544DS.h
index 9027319..71d8970 100644
--- a/include/configs/MPC8544DS.h
+++ b/include/configs/MPC8544DS.h
@@ -468,7 +468,7 @@
 
 #define CONFIG_HOSTNAME	8544ds_unknown
 #define CONFIG_ROOTPATH	"/nfs/mpc85xx"
-#define CONFIG_BOOTFILE	8544ds/uImage.uboot
+#define CONFIG_BOOTFILE	"8544ds/uImage.uboot"
 #define CONFIG_UBOOTPATH	8544ds/u-boot.bin	/* TFTP server */
 
 #define CONFIG_SERVERIP	192.168.1.1