objtool: add kunit_try_catch_throw to the noreturn list

Fix the following warning seen on GCC 7.3:
kunit/test-test.o: warning: objtool: kunit_test_unsuccessful_try() falls through to next function kunit_test_catch()

kunit_try_catch_throw is a function added in the following patch in this
series; it allows KUnit, a unit testing framework for the kernel, to
bail out of a broken test. As a consequence, it is a new __noreturn
function that objtool thinks is broken (as seen above). So fix this
warning by adding kunit_try_catch_throw to objtool's noreturn list.

Reported-by: kbuild test robot <[e-mail]>
Signed-off-by: Brendan Higgins <[e-mail]>
Acked-by: Josh Poimboeuf <[e-mail]>
Link: https://www.spinics.net/lists/linux-kbuild/msg21708.html
Cc: Peter Zijlstra <[e-mail]>
Signed-off-by: Shuah Khan <[e-mail]>

tools/objtool/check.c

···
 		"usercopy_abort",
 		"machine_real_restart",
 		"rewind_stack_do_exit",
+		"kunit_try_catch_throw",
 	};
 
 	if (!func)