fs: jffs2: add initial support for reading jffs2 ...

Import the jffs2 filesystem code from Linux v5.5-rc1 and convert it
to work with barebox.

Writing is *not* supported.

Testing was done with a n25q256a-compatible QuadSPI chip on a
SoCFPGA-based Socrates board.

Testing was done with a combination of:
	user@somelinuxhost: mkfs.jffs2 --eraseblock=4 -d fs/jffs2/ -o jffs2.img
	root@target:~ flash_erase -j /dev/mtd5 0 0
	root@target:~ dd if=jffs2.img of=/dev/mtd5
	barebox@EBV SOCrates:/ mount /dev/mtd0.data
	(...)
	mounted /dev/mtd0.data on /mnt/mtd0.data

Signed-off-by: Steffen Trumtrar <s.trumtrar@pengutronix.de>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>

remove uncompilable filesystems

Move "ar" flags to config.mk to allow for silent "make -s" ...

Based on patch by Mike Frysinger, 20 Jun 2006

Add support for a saving build objects in a separate directory. ...

Modifications are based on the linux kernel approach and
support two use cases:

  1) Add O= to the make command line
  'make O=/tmp/build all'

  2) Set environement variable BUILD_DIR to point to the desired location
  'export BUILD_DIR=/tmp/build'
  'make'

The second approach can also be used with a MAKEALL script
'export BUILD_DIR=/tmp/build'
'./MAKEALL'

Command line 'O=' setting overrides BUILD_DIR environent variable.

When none of the above methods is used the local build is performed and
the object files are placed in the source directory.

Major upate of JFFS2 code; now in sync with snapshot of MTD CVS of ...

March 13, 2005); new configuration options CONFIG_JFFS2_LZO and
CONFIG_JFFS2_LZARI are added. Both are undefined by default.

Initial revision