g: corrected division algorithm in DCRYPTO_bn_div
g: corrected division algorithm in DCRYPTO_bn_div

Long division algorithm computes incorrect answer in rare cases causing
valid RSA signatures to be rejected.

BRANCH=cr50
BUG=b:137973895
TEST=tpm_test passes

Change-Id: Ie8f39eed21443978734adbbf60b72d7701154c18
Signed-off-by: Vadim Sukhomlinov <16dcec814cb2dd6842461ffe338f55a390222303@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/ec/+/1766088
Reviewed-by: Vadim Bendebury <5515d6d2d0829cbe0dd0dcf2094aaded06d58514@chromium.org>
Reviewed-by: Andrey Pronin <53bbebe6910b11f7aa2d1daaa466658eb4cba5f2@chromium.org>

coreboot/chrome-ec,coreboot/chrome-ec,coreboot/chrome-ec,coreboot/chrome-ec,coreboot/chrome-ec,coreboot/chrome-ec