tpm2: fix GCC 15 stringop-overflow error in MakeIv

When compiling with GCC 15 using `CFLAGS=-march=x86-64-v4`, the compiler's
aggressively optimized vectorizer triggers a false-positive
-Wstringop-overflow error. Because x86-64-v4 enables wide AVX-512 registers,
the compiler misinterprets the loop unrolling and warns that a 64-byte
vector write is overflowing the destination buffer:
```
  tpm2/TPMCmd/tpm/src/crypt/AlgorithmTests.c:158:17: error: 
  writing 64 bytes into a region of size 15 [-Werror=stringop-overflow=]
    158 |             *iv = i;
```

This fixes the warning by marking the `iv` output pointer parameter as
`volatile`. This inhibits the over-aggressive loop vectorization on this
specific buffer, silencing the compiler error without changing the
underlying logic.

Signed-off-by: Arthur Gautier <arthur.gautier@arista.com>

src/tpm2/TPMCmd/tpm/src/crypt/AlgorithmTests.c

@@ -138,9 +138,9 @@ TestSMAC(
 
 //*** MakeIv()
 // Internal function to make the appropriate IV depending on the mode.
-static UINT32 MakeIv(TPM_ALG_ID mode,  // IN: symmetric mode
-                     UINT32     size,  // IN: block size of the algorithm
-                     BYTE*      iv     // OUT: IV to fill in
+static UINT32 MakeIv(TPM_ALG_ID     mode,  // IN: symmetric mode
+                     UINT32         size,  // IN: block size of the algorithm
+                     volatile BYTE* iv     // OUT: IV to fill in; 'volatile' for gcc15
 )
 {
     BYTE i;