Use default amount of inodes for block device (!1841)

This fixes #1845 without breaking #1717 (closed). The amount of inodes
only needs to be explicitly set when we don't know the size of the
filesystem before hand, for example when using fastboot or Heimdall. In
all other cases it's actually better to let it figure out automatically
how many inodes is set.

On my 16GB sdcard the amount of available inodes got increased by 10
times (from ~100K to ~1M).

pmb/install/format.py

@@ -70,9 +70,16 @@ def format_and_mount_pm_crypt(args):
         # Some downstream kernels don't support metadata_csum (#1364).
         # When changing the options of mkfs.ext4, also change them in the
         # recovery zip code (see 'grep -r mkfs\.ext4')!
-        pmb.chroot.root(args, ["mkfs.ext4", "-O", "^metadata_csum", "-F",
-                               "-q", "-L", "pmOS_root", "-N", "100000",
-                               device])
+        mkfs_ext4_args = ["mkfs.ext4", "-O", "^metadata_csum", "-F",
+                          "-q", "-L", "pmOS_root"]
+
+        # When we don't know the file system size before hand like
+        # with non-block devices, we need to explicitely set a number of
+        # inodes. See #1717 and #1845 for details
+        if not args.sdcard:
+            mkfs_ext4_args = mkfs_ext4_args + ["-N", "100000"]
+
+        pmb.chroot.root(args, mkfs_ext4_args + [device])
 
     # Mount
     mountpoint = "/mnt/install"