Wait states are signaled in the last byte received from the TPM in
response to the header, not the first byte. Check rx_buf[3] instead of
rx_buf[0].

Cc: <stable@vger.kernel.org>
Fixes: 0edbfea5 ("tpm/tpm_tis_spi: Add support for spi phy")
Signed-off-by: NAlexander Steffen <Alexander.Steffen@infineon.com>
Signed-off-by: NPeter Huewe <peter.huewe@infineon.com>
Reviewed-by: NJarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
Tested-by: NBenoit Houyere <benoit.houyere@st.com>
Signed-off-by: NJarkko Sakkinen <jarkko.sakkinen@linux.intel.com>