wic: add /boot mount point to fstab by default

wic avoided adding /boot to fstab for no reason.
This exception was hardcoded in the wic code.

There is no need for this as mountpoint in .wks file is an optional
field. It can be used only if user wants to have partitions
automatically mounted on system boot.

[YOCTO #11662]

(From OE-Core rev: 2376b05512ddb8c4ec3aaf1df11071f536a76bd9)

Signed-off-by: Ed Bartosh <ed.bartosh@linux.intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

scripts/lib/wic/plugins/imager/direct.py

@@ -135,7 +135,7 @@ class DirectPlugin(ImagerPlugin):
         updated = False
         for part in parts:
             if not part.realnum or not part.mountpoint \
-               or part.mountpoint in ("/", "/boot"):
+               or part.mountpoint == "/":
                 continue
 
             # mmc device partitions are named mmcblk0p1, mmcblk0p2..