racehound: fix kernel module compile

- check for linux kernel >= 3.14
- add cross compile enviornment for linux kernel compile
- add additional kernel config hint (CONFIG_KALLSYMS_ALL)
- fix kernel module install path

[Thomas:
 - fix Config.in dependency logic for the comment on the kernel
   version, as noticed by Baruch.
 - minor improvements in the .mk file.]

Signed-off-by: Peter Seiderer <ps.report@gmx.net>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>