spi/tpm: read TPM version in larger chunks

The TPM version string has become much longer recently, and the
TPM_FW_VER register available on VID 1ae0 devices supports reading in
arbitrary size quantities.

Let's read 50 bytes at a time to reduce the SPI register read wrapper
overhead, and increase the length limit to 300 bytes to accommodate
longer version strings.

TEST=verified on the Kevin device:
 localhost ~ # grep cr50 /sys/firmware/log
 Firmware version: RO_A: 0.0.1/84e2dde7 RO_B:* 0.0.2/13eda43f RW_A:* cr50_v1.1.5005-444ddb7 RW_B: cr50_v1.1.5005-5aac83c
 cr50_v1.1.5005-444ddb7 private-cr51:v0.0.66-bd9a0fe tpm2:v0.0.259-8f3d735 cryptoc:v0.0.4-5319e83 2016-07-31 10:58:05 vbendeb@kvasha

Change-Id: Ifaf28c1a9a3990372a9cec108c098edbe50d3243
Signed-off-by: Vadim Bendebury <vbendeb@chromium.org>
Reviewed-on: https://review.coreboot.org/16000
Tested-by: build bot (Jenkins)
Reviewed-by: Aaron Durbin <adurbin@chromium.org>

0 files changed, 0 insertions, 0 deletions