Correct ipp-crypto submodule branch name (#1060)

Only change branch name displayed in `.gitmodules`.
No change to submodule commit or source code.

Signed-off-by: Li, Xun <xun.li@intel.com>

.gitmodules

@@ -12,7 +12,7 @@
 [submodule "ipp-crypto"]
 	path = external/ippcp_internal/ipp-crypto
 	url = https://github.com/intel/ipp-crypto.git
-	branch = ipp-crypto_2021_10_0
+	branch = ipp-crypto_2021_12_1
 [submodule "external/protobuf/protobuf_code"]
 	path = external/protobuf/protobuf_code
 	url = https://github.com/protocolbuffers/protobuf.git