wic: added fspassno parameter to partition

wic: added fspassno parameter to partition

The `fspassno` parameter allows to overwrite the value of the last
column (`fs_passno`) in the /etc/fstab of the target root file system.
This allows to have periodic file system checks.

Signed-off-by: Claudius Heine <ch@denx.de>
Signed-off-by: Vijai Kumar K <Vijaikumar_Kanagarajan@mentor.com>
Signed-off-by: Luca Ceresoli <luca.ceresoli@bootlin.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>