shared: Add timespec_eq helper function

Add a helper function to check if two struct timespec values are equal.
This helper function will be used in upcoming commits that implement the
input_timestamps_unstable_v1 protocol.

Signed-off-by: Alexandros Frantzis <alexandros.frantzis@collabora.com>
Reviewed-by: Pekka Paalanen <pekka.paalanen@collabora.co.uk>

tests/timespec-test.c

@@ -294,3 +294,15 @@ ZUC_TEST(timespec_test, timespec_is_zero)
 	ZUC_ASSERT_FALSE(timespec_is_zero(&non_zero_nsec));
 	ZUC_ASSERT_FALSE(timespec_is_zero(&non_zero_sec));
 }
+
+ZUC_TEST(timespec_test, timespec_eq)
+{
+	struct timespec a = { .tv_sec = 2, .tv_nsec = 1 };
+	struct timespec b = { .tv_sec = -1, .tv_nsec = 2 };
+
+	ZUC_ASSERT_TRUE(timespec_eq(&a, &a));
+	ZUC_ASSERT_TRUE(timespec_eq(&b, &b));
+
+	ZUC_ASSERT_FALSE(timespec_eq(&a, &b));
+	ZUC_ASSERT_FALSE(timespec_eq(&b, &a));
+}