kvmtool: add patch to fix build with musl

This commit backports an upstream patch that fixes the build of
kvmtool with musl:

In file included from builtin-balloon.c:9:0:
include/kvm/kvm.h:22:0: warning: "PAGE_SIZE" redefined
 #define PAGE_SIZE (sysconf(_SC_PAGE_SIZE))

Fixes one part of:

  http://autobuild.buildroot.net/results/4459a909e735343d1cf768d30466bc3c57eca19e/



Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Tested-by: Bernd Kuhls <bernd.kuhls@t-online.de>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>