Fix format-truncation compile failure by typecasting USB IDs (#8250)

This patch adds safe_atoux16 for parsing an unsigned hexadecimal 16bit int, and
uses that for parsing USB device and vendor IDs.

This fixes a compile error with gcc-8 because while we know that USB IDs are 2 bytes,
the compiler does not know that.

../src/udev/udev-builtin-hwdb.c:80:38: error: '%04X' directive output may be
truncated writing between 4 and 8 bytes into a region of size between 2 and 6
[-Werror=format-truncation=]

Signed-off-by: Adam Williamson <awilliam@redhat.com>
Signed-off-by: Patrick Uiterwijk <puiterwijk@redhat.com>

src/test/test-parse-util.c

@@ -468,6 +468,44 @@ static void test_safe_atoi16(void) {
         assert_se(r == -EINVAL);
 }
 
+static void test_safe_atoux16(void) {
+        int r;
+        uint16_t l;
+
+        r = safe_atoux16("1234", &l);
+        assert_se(r == 0);
+        assert_se(l == 0x1234);
+
+        r = safe_atoux16("abcd", &l);
+        assert_se(r == 0);
+        assert_se(l == 0xabcd);
+
+        r = safe_atoux16("  1234", &l);
+        assert_se(r == 0);
+        assert_se(l == 0x1234);
+
+        r = safe_atoux16("12345", &l);
+        assert_se(r == -ERANGE);
+
+        r = safe_atoux16("-1", &l);
+        assert_se(r == -ERANGE);
+
+        r = safe_atoux16("  -1", &l);
+        assert_se(r == -ERANGE);
+
+        r = safe_atoux16("junk", &l);
+        assert_se(r == -EINVAL);
+
+        r = safe_atoux16("123x", &l);
+        assert_se(r == -EINVAL);
+
+        r = safe_atoux16("12.3", &l);
+        assert_se(r == -EINVAL);
+
+        r = safe_atoux16("", &l);
+        assert_se(r == -EINVAL);
+}
+
 static void test_safe_atou64(void) {
         int r;
         uint64_t l;
@@ -745,6 +783,7 @@ int main(int argc, char *argv[]) {
         test_safe_atolli();
         test_safe_atou16();
         test_safe_atoi16();
+        test_safe_atoux16();
         test_safe_atou64();
         test_safe_atoi64();
         test_safe_atod();