dpdk: update spdk/dpdk 21.08 submodule

Update submodule after recent fixes related to Clang-13.
https://github.com/spdk/dpdk/commit/6af54b79a4b5fca6e72020db21cd0f43f44dcd56
https://github.com/spdk/dpdk/commit/a3c2b3951bd36f1907e2db960e353e23e15d7f4e
https://github.com/spdk/dpdk/commit/bda789a357a8f34521bb1d9d223d8d044dd09be4



Signed-off-by: Karol Latecki <karol.latecki@intel.com>
Change-Id: Iee036ed0890d462bf028508d1dd0890b9f9ea9a8
Reviewed-on: https://review.spdk.io/gerrit/c/spdk/spdk/+/10637


Reviewed-by: Tomasz Zawadzki <tomasz.zawadzki@intel.com>
Reviewed-by: Jim Harris <james.r.harris@intel.com>
Reviewed-by: Aleksey Marchuk <alexeymar@mellanox.com>
Community-CI: Mellanox Build Bot
Tested-by: SPDK CI Jenkins <sys_sgci@intel.com>