init-storage: Add retry loop for findfs

Occasionally, especially on a Raspberry Pi, the storage subsystem has
not fully enumerated all of the disks before the `init-storage` script
starts.  This prevents the system from being able to boot, since the
script attempts to identify the root filesystem very early.  Now, we try
a few times to identify the filesystem before giving up, to give the
kernel a chance to discover everything.

boot/initramfs/init-storage.sh

@@ -28,6 +28,16 @@ copy_vol() {
     umount "${tmpdir}"
 }
 
+find_part() {
+    _i=0
+    while [ $_i -lt 5 ]; do
+        findfs "$1" 2>/dev/null && return
+        _i=$((_i + 1))
+        sleep 1
+    done
+    findfs "$1"
+}
+
 format_dev() {
     dev="$1"
     partno=$(partition_number "${dev}")
@@ -140,8 +150,8 @@ setup_etc() {
         /sysroot/etc
 }
 
-rootdev=$(findfs "$1")
-datapart=$(findfs "${2:-PARTLABEL=aimeeos-data}")
+rootdev=$(find_part "$1")
+datapart=$(find_part "${2:-PARTLABEL=aimeeos-data}")
 if [ -b "${datapart}" ]; then
     printf 'Found data partition: %s\n' "${datapart}" >&2
 else