[kvmfr] added the ability to obtain a dmabuf of the ivshmem memory

This is to enable the ability to use dri3 to create dmabuf backed
pixmaps directly.

module/test.c

@@ -0,0 +1,52 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <unistd.h>
+#include <string.h>
+#include <fcntl.h>
+#include <unistd.h>
+#include <string.h>
+#include <sys/ioctl.h>
+#include <sys/syscall.h>
+#include <sys/mman.h>
+
+#include "kvmfr.h"
+
+int main()
+{
+  int fd = open("/dev/kvmfr0", O_RDWR);
+  if (fd < 0)
+  {
+    perror("open");
+    return -1;
+  }
+
+  unsigned long size      = ioctl(fd, KVMFR_DMABUF_GETSIZE , 0);
+  unsigned long alignment = ioctl(fd, KVMFR_DMABUF_GETALIGN, 0);
+
+  printf("Size: %lu MiB, Alignment: %lu MiB\n", size / 1024 / 1024, alignment / 1024 / 1024);
+
+  struct kvmfr_dmabuf_create create =
+  {
+    .flags  = KVMFR_DMABUF_FLAG_CLOEXEC,
+    .offset = 0x0,
+    .size   = size,
+  };
+  int dmaFd = ioctl(fd, KVMFR_DMABUF_CREATE, &create);
+  if (dmaFd < 0)
+  {
+    perror("ioctl");
+    return -1;
+  }
+
+  void * mem = mmap(NULL, create.size, PROT_READ | PROT_WRITE, MAP_SHARED, dmaFd, 0);
+  if (!mem)
+  {
+    perror("mmap");
+    return -1;
+  }
+
+  memset(mem, 0xAA, create.size);
+  munmap(mem, create.size);
+  close(fd);
+  return 0;
+}