fix off-by-one error in CheckOverflow
fix off-by-one error in CheckOverflow

The overflow check as provided by CheckOverflow contains an off-by-one
error causing an out-of-bounds read by one byte to not be detected
properly. The used size should be calculated as
  usedSize = (INT64)(nextData - buffer) + size;
and not
  usedSize = (INT64)(nextData - buffer) - 1 + size;

For the latter case, consider the attempt of reading the very first two
bytes from a buffer of one byte size. 'usedSize' will be 1 (0x1000 -
0x1000 - 1 + 2). Because 'usedSize' is not greater than 'bufferSize'
(also 1), we will not detect the out-of-bounds read.
This change fixes the issue by removing the addend of -1.

01org/TPM2.0-TSS,01org/tpm2-tss,01org/TPM2.0-TSS,01org/tpm2-tss,tpm2-software/tpm2-tss,tpm2-software/tpm2-tss,tpm2-software/tpm2-tss,01org/tpm2-tss,01org/TPM2.0-TSS,01org/TPM2.0-TSS