test_suite_ecp: Added `MBEDTLS_ECP_NIST_OPTIM` define guards.

This patch updates `ecp_mod_p_generic_raw` and corresponding
curve test methods, that depend on the NIST optimisation
parameter to not run when it is not included.

The following curves are affected:
* SECP192R1
* SECP224R1
* SECP256R1
* SECP384R1
* SECP521R1

Signed-off-by: Minos Galanakis <minos.galanakis@arm.com>
diff --git a/tests/suites/test_suite_ecp.function b/tests/suites/test_suite_ecp.function
index 1df0624..55ded45 100644
--- a/tests/suites/test_suite_ecp.function
+++ b/tests/suites/test_suite_ecp.function
@@ -1294,35 +1294,35 @@
     bytes = limbs_N * sizeof(mbedtls_mpi_uint);
 
     switch (curve_id) {
-#if defined(MBEDTLS_ECP_DP_SECP192R1_ENABLED)
+#if defined(MBEDTLS_ECP_DP_SECP192R1_ENABLED) && defined(MBEDTLS_ECP_NIST_OPTIM)
         case MBEDTLS_ECP_DP_SECP192R1:
             limbs = 2 * limbs_N;
             curve_bits = 192;
             curve_func = &mbedtls_ecp_mod_p192_raw;
             break;
 #endif
-#if defined(MBEDTLS_ECP_DP_SECP224R1_ENABLED)
+#if defined(MBEDTLS_ECP_DP_SECP224R1_ENABLED) && defined(MBEDTLS_ECP_NIST_OPTIM)
         case MBEDTLS_ECP_DP_SECP224R1:
             limbs = 448 / biL;
             curve_bits = 224;
             curve_func = &mbedtls_ecp_mod_p224_raw;
             break;
 #endif
-#if defined(MBEDTLS_ECP_DP_SECP256R1_ENABLED)
+#if defined(MBEDTLS_ECP_DP_SECP256R1_ENABLED) && defined(MBEDTLS_ECP_NIST_OPTIM)
         case MBEDTLS_ECP_DP_SECP256R1:
             limbs = 2 * limbs_N;
             curve_bits = 256;
             curve_func = &mbedtls_ecp_mod_p256_raw;
             break;
 #endif
-#if defined(MBEDTLS_ECP_DP_SECP384R1_ENABLED)
+#if defined(MBEDTLS_ECP_DP_SECP384R1_ENABLED) && defined(MBEDTLS_ECP_NIST_OPTIM)
         case MBEDTLS_ECP_DP_SECP384R1:
             limbs = 2 * limbs_N;
             curve_bits = 384;
             curve_func = &mbedtls_ecp_mod_p384_raw;
             break;
 #endif
-#if defined(MBEDTLS_ECP_DP_SECP521R1_ENABLED)
+#if defined(MBEDTLS_ECP_DP_SECP521R1_ENABLED) && defined(MBEDTLS_ECP_NIST_OPTIM)
         case MBEDTLS_ECP_DP_SECP521R1:
             limbs = 2 * limbs_N;
             curve_bits = 522;