src/meta-openembedded:memtool: Add recipe

memtool is a program that allows to access memory mapped registers.
This is useful to inspect and modify registers from the command line.
memtool can also operate on plain files, and access PHY registers.

Signed-off-by: Ricardo Simoes <ricardo.simoespt.bosch.com>
Signed-off-by: Mark Jonas <mark.jonasde.bosch.com>
Signed-off-by: Khem Raj <raj.khemgmail.com>