livepatch: Add support for modules .modinfo section metadata

livepatch: Add support for modules .modinfo section metadata

Having detailed livepatch metadata helps to properly identify module's
origin and version. It also allows to keep track of the history of
livepatch loads in the system (at least within dmesg buffer size
limits).

The livepatch metadata are embedded in a form of .modinfo section.
Each such section contains data of the following format:
key=value\0key=value\0...key=value\0

The .modinfo section may be generated and appended to the resulting
livepatch ELF file optionally as an extra step of a higher level
livepatch build system.

The metadata section pointer and the section length is stored in the
livepatch payload structure and is used to display the content upon
livepatch apply operation.

Signed-off-by: Pawel Wieczorkiewicz <wipawel@amazon.de>
Reviewed-by: Andra-Irina Paraschiv <andraprs@amazon.com>
Reviewed-by: Bjoern Doebel <doebel@amazon.de>
Reviewed-by: Leonard Foerster <foersleo@amazon.de>
Reviewed-by: Martin Pohlack <mpohlack@amazon.de>
Reviewed-by: Norbert Manthey <nmanthey@amazon.de>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Reviewed-by: Ross Lagerwall <ross.lagerwall@citrix.com>