buildroot

mtd: add option to install mtd integrity test

The mtd tests have proven very useful in testing both flash stability
and JFFS2 changes. Adding an option to install the integrity test.

Signed-off-by: Yugendra Sai Babu Nadupuru <yugendra.sai.babu.nadupuru@rockwellcollins.com>
Signed-off-by: Matt Weber <matthew.weber@rockwellcollins.com>
[Thomas: rename Config.in option, misc improvements in .mk file, add
patch to fix build with uClibc/musl.]
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>