make build_info fixed-length
make build_info fixed-length

This makes build_info fixed-length so that it can be properly
transmitted via I2C. The host buffer size will be used, which may
in fact be quite a bit longer than necessary.  Build info will be
truncated if it's longer than the max response size.

Signed-off-by: David Hendricks <3b0deacc4b5357f519084f1ea34bd42bf5d34545@chromium.org>
BRANCH=snow
BUG=chrome-os-partner:11608
TEST=Tested on Snow, logic analyzer confirmed NAK and STOP condition
set properly after final byte transmitted via I2C (see BUG)

Change-Id: Iccae0f3c2905d442c8eebff42aa19bf940e5f71f
Reviewed-on: https://gerrit.chromium.org/gerrit/32290
Reviewed-by: Yung-Chieh Lo <2d80bee8408e64f859a1b5868bd3b311c0a4b4cd@chromium.org>
Commit-Ready: David Hendricks <3b0deacc4b5357f519084f1ea34bd42bf5d34545@chromium.org>
Tested-by: David Hendricks <3b0deacc4b5357f519084f1ea34bd42bf5d34545@chromium.org>

fourier49/BZ_DEV_EC,fourier49/BZ_DEV_EC,fourier49/BZ_DEV_EC,gelraen/cros-ec,md5555/ec,alterapraxisptyltd/chromium-ec,akappy7/ChromeOS_EC_LED_Diagnostics,mtk09422/chromiumos-platform-ec,alterapraxisptyltd/chromium-ec,longsleep/ec,thehobn/ec,longsleep/ec,akappy7/ChromeOS_EC_LED_Diagnostics,thehobn/ec,akappy7/ChromeOS_EC_LED_Diagnostics,gelraen/cros-ec,coreboot/chrome-ec,md5555/ec,mtk09422/chromiumos-platform-ec,fourier49/BIZ_EC,fourier49/BIZ_EC,longsleep/ec,eatbyte/chromium-ec,coreboot/chrome-ec,gelraen/cros-ec,alterapraxisptyltd/chromium-ec,md5555/ec,coreboot/chrome-ec,eatbyte/chromium-ec,coreboot/chrome-ec,eatbyte/chromium-ec,fourier49/BZ_DEV_EC,eatbyte/chromium-ec,fourier49/BIZ_EC,md5555/ec,akappy7/ChromeOS_EC_LED_Diagnostics,gelraen/cros-ec,thehobn/ec,fourier49/BIZ_EC,longsleep/ec,thehobn/ec,akappy7/ChromeOS_EC_LED_Diagnostics,mtk09422/chromiumos-platform-ec,coreboot/chrome-ec,alterapraxisptyltd/chromium-ec,coreboot/chrome-ec,mtk09422/chromiumos-platform-ec