tpm: read burstcount from TPM_STS in one 32-bit transaction

tpm: read burstcount from TPM_STS in one 32-bit transaction

commit 9754d45e997000ad4021bc4606cc266bb38d876f upstream.

Some chips incorrectly support partial reads from TPM_STS register
at non-zero offsets. Read the entire 32-bits register instead of
making two 8-bit reads to support such devices and reduce the number
of bus transactions when obtaining the burstcount from TPM_STS.

Fixes: 27084efee0c3 ("tpm: driver for next generation TPM chips")
Signed-off-by: Andrey Pronin <apronin@chromium.org>
Reviewed-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
Signed-off-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
[bwh: Backported to 3.2:
 - Use raw ioread32() instead of tpm_tis_read32()
 - Adjust filename, context]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>