freedreno: add dummy fd_bo_from_fbdev implementation when KGSL is disabled

Make sure that this function is defined (even empty/dummy) when KGSL support is
disabled, since it's part of the driver i/f and it was reported to cause symbols
issues when building against musl libc implementation.

Reported-by: Khem Raj <raj.khem@gmail.com>
Signed-off-by: Nicolas Dechesne <nicolas.dechesne@linaro.org>
Signed-off-by: Rob Clark <robclark@freedesktop.org>
diff --git a/freedreno/freedreno_bo.c b/freedreno/freedreno_bo.c
index a23c65d..82c1f15 100644
--- a/freedreno/freedreno_bo.c
+++ b/freedreno/freedreno_bo.c
@@ -431,3 +431,10 @@
 {
 	bo->funcs->cpu_fini(bo);
 }
+
+#ifndef HAVE_FREEDRENO_KGSL
+struct fd_bo * fd_bo_from_fbdev(struct fd_pipe *pipe, int fbfd, uint32_t size)
+{
+    return NULL;
+}
+#endif