Use upper case for bignum string comparison

Test data which is compared as a hex string now uses upper case to
match output of mbedtls_mpi_write_string() output. This removes usage
of strcasecmp().

Signed-off-by: Werner Lewis <werner.lewis@arm.com>
diff --git a/tests/suites/test_suite_mpi.function b/tests/suites/test_suite_mpi.function
index fba19c7..a53d0cb 100644
--- a/tests/suites/test_suite_mpi.function
+++ b/tests/suites/test_suite_mpi.function
@@ -404,7 +404,7 @@
     TEST_ASSERT( mbedtls_mpi_read_binary( &X, buf->x, buf->len ) == 0 );
     TEST_ASSERT( sign_is_valid( &X ) );
     TEST_ASSERT( mbedtls_mpi_write_string( &X, 16, str, sizeof( str ), &len ) == 0 );
-    TEST_ASSERT( strcasecmp( (char *) str, input_A ) == 0 );
+    TEST_ASSERT( strcmp( (char *) str, input_A ) == 0 );
 
 exit:
     mbedtls_mpi_free( &X );
@@ -424,7 +424,7 @@
     TEST_ASSERT( mbedtls_mpi_read_binary_le( &X, buf->x, buf->len ) == 0 );
     TEST_ASSERT( sign_is_valid( &X ) );
     TEST_ASSERT( mbedtls_mpi_write_string( &X, 16, str, sizeof( str ), &len ) == 0 );
-    TEST_ASSERT( strcasecmp( (char *) str, input_A ) == 0 );
+    TEST_ASSERT( strcmp( (char *) str, input_A ) == 0 );
 
 exit:
     mbedtls_mpi_free( &X );