tpm: Fix expected number of response bytes of TPM1.2 PCR Extend

The TPM1.2 PCR Extend operation only returns 20 bytes in the body,
which is the size of the PCR state.

This fixes a problem where IMA gets errors with every PCR Extend.

Fixes: c659af78 ("tpm: Check size of response before accessing data")
Signed-off-by: Stefan Berger <stefanb@linux.vnet.ibm.com>
Acked-by: Mimi Zohar <zohar@us.ibm.com>
Reviewed-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
Signed-off-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>

drivers/char/tpm/tpm-interface.c

@@ -767,7 +767,7 @@ EXPORT_SYMBOL_GPL(tpm_pcr_read);
 
 #define TPM_ORD_PCR_EXTEND cpu_to_be32(20)
 #define EXTEND_PCR_RESULT_SIZE 34
-#define EXTEND_PCR_RESULT_BODY_SIZE 24
+#define EXTEND_PCR_RESULT_BODY_SIZE 20
 static const struct tpm_input_header pcrextend_header = {
 	.tag = TPM_TAG_RQU_COMMAND,
 	.length = cpu_to_be32(34),