treewide: Convert CONFIG_HOSTNAME to a string option

CONFIG_HOSTNAME is defined as a "plain" preprocessor string, but every
use is couched by __stringify(...).

Hence, convert it to a proper string option.

Signed-off-by: Mario Six <mario.six@gdsys.cc>
diff --git a/include/configs/mcx.h b/include/configs/mcx.h
index 045f602..27098ec 100644
--- a/include/configs/mcx.h
+++ b/include/configs/mcx.h
@@ -106,7 +106,7 @@
 
 /* Setup MTD for NAND on the SOM */
 
-#define CONFIG_HOSTNAME mcx
+#define CONFIG_HOSTNAME "mcx"
 #define CONFIG_EXTRA_ENV_SETTINGS \
 	"adddbg=setenv bootargs ${bootargs} trace_buf_size=64M\0"	\
 	"adddebug=setenv bootargs ${bootargs} earlyprintk=serial\0"	\
@@ -125,13 +125,13 @@
 	"addmtd=setenv bootargs ${bootargs} ${mtdparts}\0"		\
 	"baudrate=115200\0"						\
 	"consoledev=ttyO2\0"						\
-	"hostname=" __stringify(CONFIG_HOSTNAME) "\0"			\
+	"hostname=" CONFIG_HOSTNAME "\0"			\
 	"loadaddr=0x82000000\0"						\
 	"load=tftp ${loadaddr} ${u-boot}\0"				\
 	"load_k=tftp ${loadaddr} ${bootfile}\0"				\
 	"loaduimage=fatload mmc 0 ${loadaddr} uImage\0"			\
 	"loadmlo=tftp ${loadaddr} ${mlo}\0"				\
-	"mlo=" __stringify(CONFIG_HOSTNAME) "/MLO\0"			\
+	"mlo=" CONFIG_HOSTNAME "/MLO\0"			\
 	"mmcargs=root=/dev/mmcblk0p2 rw "				\
 		"rootfstype=ext3 rootwait\0"				\
 	"mmcboot=echo Booting from mmc ...; "				\
@@ -145,7 +145,7 @@
 		"bootm ${loadaddr}\0"					\
 	"nfsargs=setenv bootargs root=/dev/nfs rw "			\
 		"nfsroot=${serverip}:${rootpath}\0"			\
-	"u-boot=" __stringify(CONFIG_HOSTNAME) "/u-boot.img\0"		\
+	"u-boot=" CONFIG_HOSTNAME "/u-boot.img\0"		\
 	"uboot_addr=0x80000\0"						\
 	"update=nandecc sw;nand erase ${uboot_addr} 100000;"		\
 		"nand write ${loadaddr} ${uboot_addr} 80000\0"		\