init: create /mnt/sdcard if not present

PR #38 was merged a bit too early, as there's a case when this directory
does not exist at mount time. In addition, move mounting before printing
the banner just because it outputs some messages to syslog.

Closes #38

tp2bmc/board/tp2bmc/overlay/etc/init.d/S99hello.sh

@@ -1,17 +1,19 @@
 #! /bin/sh
 
+mkdir -p /mnt/sdcard
+
+if [ -b /dev/mmcblk0p1 ]; then
+    mount /dev/mmcblk0p1 /mnt/sdcard
+elif [ -b /dev/mmcblk0 ]; then
+    mount /dev/mmcblk0 /mnt/sdcard
+fi
+
 echo " _____ _   _ ____  ___ _   _  ____ "
 echo "|_   _| | | |  _ \|_ _| \ | |/ ___|"
 echo "  | | | | | | |_) || ||  \| | |  _ "
 echo "  | | | |_| |  _ < | || |\  | |_| |"
 echo "  |_|  \___/|_| \_\___|_| \_|\____|"
 
-if [ -f /dev/mmcblk0p1 ]; then
-    mount /dev/mmcblk0p1 /mnt/sdcard/
-elif [ -f /dev/mmcblk0 ]; then
-    mount /dev/mmcblk0 /mnt/sdcard/
-fi
-
 echo 3 4 1 7 > /proc/sys/kernel/printk
 
 sleep 1