unit: Fix gcc warning

In file included from unit/test-mbim.c:28:0:
unit/test-mbim.c: In function ‘parse_device_caps’:
unit/test-mbim.c:332:9: error: suggest parentheses around assignment used as truth value [-Werror=parentheses]
  assert(cellular_class = 1);

1 files changed, 1 insertions, 1 deletions

diff --git a/unit/test-mbim.c b/unit/test-mbim.c
index a4ac8541..b27bfb2a 100644
--- a/unit/test-mbim.c
+++ b/unit/test-mbim.c
@@ -329,7 +329,7 @@ static void parse_device_caps(const void *data)
 	assert(r);
 
 	assert(device_type == 1);
-	assert(cellular_class = 1);
+	assert(cellular_class == 1);
 	assert(voice_class == 1);
 	assert(sim_class == 2);
 	assert(data_class == 0x3f);