omap3_beagle: enable the use of a plain text file

Using the new env import command it is possible to use plain text files instead
of script-images. Plain text files are much easier to handle.

E.g. If your boot.scr contains the following:
-----------------------------------
setenv dvimode 1024x768-16@60
run loaduimage
run mmcboot
-----------------------------------
you could create a file named uEnv.txt and use that instead of boot.scr:
-----------------------------------
dvimode=1024x768-16@60
uenvcmd=run loaduimage; run mmcboot
-----------------------------------
The variable uenvcmd (if existent) will be executed (using run) after uEnv.txt
was loaded. If uenvcmd doesn't exist the default boot sequence will be started,
therefore you could just use
-----------------------------------
dvimode=1024x768-16@60
-----------------------------------
as uEnv.txt because loaduimage and mmcboot is part of the default boot sequence

Signed-off-by: Jason Kridner <jkridner@beagleboard.org>
Signed-off-by: Sandeep Paulraj <s-paulraj@ti.com>

include/configs/omap3_beagle.h

@@ -228,9 +228,9 @@
 		"omapdss.def_disp=${defaultdisplay} " \
 		"root=${nandroot} " \
 		"rootfstype=${nandrootfstype}\0" \
-	"loadbootscript=fatload mmc ${mmcdev} ${loadaddr} boot.scr\0" \
-	"bootscript=echo Running bootscript from mmc ...; " \
-		"source ${loadaddr}\0" \
+	"loadbootenv=fatload mmc ${mmcdev} ${loadaddr} uEnv.txt\0" \
+	"importbootenv=echo Importing environment from mmc ...; " \
+		"env import -t $loadaddr $filesize\0" \
 	"loaduimage=fatload mmc ${mmcdev} ${loadaddr} uImage\0" \
 	"mmcboot=echo Booting from mmc ...; " \
 		"run mmcargs; " \
@@ -242,15 +242,19 @@
 
 #define CONFIG_BOOTCOMMAND \
 	"if mmc rescan ${mmcdev}; then " \
-		"if run loadbootscript; then " \
-			"run bootscript; " \
-		"else " \
-			"if run loaduimage; then " \
-				"run mmcboot; " \
-			"else run nandboot; " \
-			"fi; " \
-		"fi; " \
-	"else run nandboot; fi"
+		"echo SD/MMC found on device ${mmcdev};" \
+		"if run loadbootenv; then " \
+			"run importbootenv;" \
+		"fi;" \
+		"if test -n $uenvcmd; then " \
+			"echo Running uenvcmd ...;" \
+			"run uenvcmd;" \
+		"fi;" \
+		"if run loaduimage; then " \
+			"run mmcboot;" \
+		"fi;" \
+	"fi;" \
+	"run nandboot;" \
 
 #define CONFIG_AUTO_COMPLETE		1
 /*