bif: bif-core: do not read past the end of NVM when parsing BIF objects

Add a length check in the non-volatile memory (NVM) BIF object
parsing function so that it does not attempt to read past the
end of the NVM address space of the BIF slave.

Change-Id: Iafd40e61e7ca0bfa2e2be95c294a0e17d5cf515c
Signed-off-by: David Collins <collinsd@codeaurora.org>