e2fsprogs: add populate-extfs.sh

e2fsprogs: add populate-extfs.sh

This script is originally from Darren Hart, it will be used for creating
the ext* filesystem from a given directory, which will replace the
genext2fs in image_types.bbclass at the moment, we may use the mke2fs to
replace this script again when it has the initial directory support.

Changes of the script:
* Rename it from mkdebugfs.sh to populate-extfs.sh
* Add a simple usage
* Add checking for the number of the parameters
* Add the "regular empty file" and "fifo" file type
* Set mode, uid and gid for the file
* Save the command lines to a file and batch run them
* Change the error message
* Improve the performance
* Add the support for hardlink

[YOCTO #3848]

(From OE-Core rev: 265f91149aa8c475ebe5b7069044ed94b7857fa9)

Signed-off-by: Darren Hart <dvhart@linux.intel.com>
Signed-off-by: Robert Yang <liezhi.yang@windriver.com>
Signed-off-by: Saul Wold <sgw@linux.intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>