board/beaglebone: replace utf-8 graphic sympols by ascii characters

Signed-off-by: Peter Seiderer <ps.report@gmx.net>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>

board/beaglebone/readme.txt

@@ -27,18 +27,18 @@ $ make
 Result of the build
 ===================
 output/images/
-├── am335x-boneblack.dtb
-├── am335x-bone.dtb
-├── am335x-evm.dtb
-├── am335x-evmsk.dtb
-├── boot.vfat
-├── MLO
-├── rootfs.ext2
-├── rootfs.tar
-├── sdcard.img
-├── u-boot.img
-├── uEnv.txt
-└── zImage
++-- am335x-boneblack.dtb
++-- am335x-bone.dtb
++-- am335x-evm.dtb
++-- am335x-evmsk.dtb
++-- boot.vfat
++-- MLO
++-- rootfs.ext2
++-- rootfs.tar
++-- sdcard.img
++-- u-boot.img
++-- uEnv.txt
++-- zImage
 
 To copy the image file to the sdcard use dd:
 $ dd if=output/images/sdcard.img of=/dev/XXX