Modify mk_am335x_sdboot.sh by using new version sfdisk command which need -uM as…

Modify mk_am335x_sdboot.sh by using new version sfdisk command which need -uM as parameter to set unit of disk size.

mk_am335x_sdboot.sh

@@ -14,8 +14,8 @@ KERNEL_SIZE=2048
 ## Erase partition table
 dd if=/dev/zero of=${DEV_NODE} bs=1024 count=1
 
-sfdisk --force ${DEV_NODE} << EOF
-,${KERNEL_SIZE}M,0c,*
+sfdisk --force -uM ${DEV_NODE} << EOF
+,${KERNEL_SIZE},0c,*
 ,,83
 EOF