Since kernel 4.15, setup_timer is no more available and compilation fails with :
make -C kernel
make[1]: Entering directory '/.../wr-starting-kit/spec-sw/kernel'
make -C /lib/modules/4.18.0-1-amd64/build M=/.../wr-starting-kit/spec-sw/kernel FMC_BUS_ABS=/.../wr-starting-kit/spec-sw/fmc-bus modules
make[2]: Entering directory '/usr/src/linux-headers-4.18.0-1-amd64'
  CC [M]  /.../wr-starting-kit/spec-sw/kernel/wr_nic/endpoint.o
/.../wr-starting-kit/spec-sw/kernel/wr_nic/endpoint.c: In function 'wrn_ep_open':
/.../wr-starting-kit/spec-sw/kernel/wr_nic/endpoint.c:193:2: error: implicit declaration of function 'setup_timer'; did you mean 'del_timer'? [-Werror=implicit-function-declaration]
  setup_timer(&ep->ep_link_timer, wrn_ep_check_link, timerarg);
  ^~~~~~~~~~~
  del_timer
cc1: some warnings being treated as errors
make[5]: *** [/usr/src/linux-headers-4.18.0-1-common/scripts/Makefile.build:323: /.../wr-starting-kit/spec-sw/kernel/wr_nic/endpoint.o] Error 1
make[4]: *** [/usr/src/linux-headers-4.18.0-1-common/Makefile:1518: _module_/.../wr-starting-kit/spec-sw/kernel] Error 2
make[3]: *** [Makefile:146: sub-make] Error 2
make[2]: *** [Makefile:8: all] Error 2
make[2]: Leaving directory '/usr/src/linux-headers-4.18.0-1-amd64'
make[1]: *** [Makefile:20: all] Error 2
make[1]: Leaving directory '/.../wr-starting-kit/spec-sw/kernel'
make: *** [Makefile:28: kernel] Error 2

This patch add preprocessor case to detect kernel version.
For kernel > 4.15 timer_setup is use instead of setup_timer and callback is
adapted to the new need.
Signed-off-by: Gwenhael Goavec-Merou <gwenhael.goavec-merou@trabucayre.com>