block/export/fuse.c: fix musl build

block/export/fuse.c: fix musl build

Include linux/falloc.h if CONFIG_FALLOCATE_ZERO_RANGE is defined to fix
https://gitlab.com/qemu-project/qemu/-/commit/50482fda98bd62e072c30b7ea73c985c4e9d9bbb
and avoid the following build failure on musl:

../block/export/fuse.c: In function 'fuse_fallocate':
../block/export/fuse.c:643:21: error: 'FALLOC_FL_ZERO_RANGE' undeclared (first use in this function)
  643 |     else if (mode & FALLOC_FL_ZERO_RANGE) {
      |                     ^~~~~~~~~~~~~~~~~~~~

Fixes:
 - http://autobuild.buildroot.org/results/be24433a429fda681fb66698160132c1c99bc53b

Fixes: 50482fda98b ("block/export/fuse.c: fix musl build")
Signed-off-by: Fabrice Fontaine <fontaine.fabrice@gmail.com>
Message-Id: <20211022095209.1319671-1-fontaine.fabrice@gmail.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>