spdk: update SPDK to fix the build failure on aarch64

to include 29be88fab6bb026df27c93ee89c61965b3c43133 which addresses a
build failure on aarch64.

Signed-off-by: Kefu Chai <kchai@redhat.com>

diff --git a/src/spdk b/src/spdk
index 93bd60e0de6b161567182d965239735bf467e85c..601bcbcf666516cd6a3e3a0b515d4ea477485187 160000 (submodule)
--- a/src/spdk
+++ b/src/spdk
@@ -1 +1 @@
-Subproject commit 93bd60e0de6b161567182d965239735bf467e85c
+Subproject commit 601bcbcf666516cd6a3e3a0b515d4ea477485187