package/libkcapi: fix build on riscv32

Fix the following build failure on riscv32:

lib/internal.h:331:20: error: '__NR_io_getevents' undeclared (first use in this function); did you mean 'io_getevents'?
  331 |     return syscall(__NR_io_getevents, ctx, min, max, events, timeout);
      |                    ^~~~~~~~~~~~~~

Fixes:
 - http://autobuild.buildroot.org/results/c828d4330a8888fe8db4299dc2f20759947f329f



Signed-off-by: Fabrice Fontaine <fontaine.fabrice@gmail.com>
Signed-off-by: Arnout Vandecappelle (Essensium/Mind) <arnout@mind.be>