tpm: export tpm2_sessions_init() to fix ibmvtpm building

Commit 08d08e2e ("tpm: ibmvtpm: Call tpm2_sessions_init() to
initialize session support") adds call to tpm2_sessions_init() in ibmvtpm,
which could be built as a module. However, tpm2_sessions_init() wasn't
exported, causing libmvtpm to fail to build as a module:

ERROR: modpost: "tpm2_sessions_init" [drivers/char/tpm/tpm_ibmvtpm.ko] undefined!

Export tpm2_sessions_init() to resolve the issue.

Cc: stable@vger.kernel.org # v6.10+
Reported-by: kernel test robot <lkp@intel.com>
Closes: https://lore.kernel.org/oe-kbuild-all/202408051735.ZJkAPQ3b-lkp@intel.com/
Fixes: 08d08e2e ("tpm: ibmvtpm: Call tpm2_sessions_init() to initialize session support")
Signed-off-by: Kexy Biscuit <kexybiscuit@aosc.io>
Signed-off-by: Mingcong Bai <jeffbai@aosc.io>
Reviewed-by: Stefan Berger <stefanb@linux.ibm.com>
Reviewed-by: Jarkko Sakkinen <jarkko@kernel.org>
Signed-off-by: Jarkko Sakkinen <jarkko@kernel.org>

drivers/char/tpm/tpm2-sessions.c

@@ -1362,4 +1362,5 @@ int tpm2_sessions_init(struct tpm_chip *chip)
 
 	return rc;
 }
+EXPORT_SYMBOL(tpm2_sessions_init);
 #endif /* CONFIG_TCG_TPM2_HMAC */