CBMC: Increase the CBMC_OBJECT_BITS of matvec_mul to 12

- During latest change about adding derandomized config guard, the CBMC proof for `matvec_mul` failed due to SMT-solver return unknown,
  increadse the CBMC_OBJECT_BITS to fixed it.

Signed-off-by: willieyz <[email protected]>

Author: willieyz

proofs/cbmc/matvec_mul/Makefile

@@ -47,7 +47,7 @@ FUNCTION_NAME = mlk_matvec_mul
 # EXPENSIVE = true
 
 # This function is large enough to need...
-CBMC_OBJECT_BITS = 10
+CBMC_OBJECT_BITS = 12
 
 # If you require access to a file-local ("static") function or object to conduct
 # your proof, set the following (and do not include the original source file