Infineon TPM: Fix potential buffer overruns

Ensure that the Infineon I2C and SPI TPM driver performs adequate
validation of the length extracted from the TPM response header.
This patch prevents integer underflow when the length was too small,
which could lead to memory corruption.

Signed-off-by: Jeremy Boone <jeremy.boone@nccgroup.trust>

drivers/tpm/tpm_tis_infineon.c

@@ -374,7 +374,8 @@ static int tpm_tis_i2c_recv(struct udevice *dev, u8 *buf, size_t count)
 {
 	struct tpm_chip *chip = dev_get_priv(dev);
 	int size = 0;
-	int expected, status;
+	int status;
+	unsigned int expected;
 	int rc;
 
 	status = tpm_tis_i2c_status(dev);
@@ -394,7 +395,7 @@ static int tpm_tis_i2c_recv(struct udevice *dev, u8 *buf, size_t count)
 	}
 
 	expected = get_unaligned_be32(buf + TPM_RSP_SIZE_BYTE);
-	if ((size_t)expected > count) {
+	if ((size_t)expected > count || (size_t)expected < TPM_HEADER_SIZE) {
 		debug("Error size=%x, expected=%x, count=%x\n", size, expected,
 		      count);
 		return -ENOSPC;