modpost.c: Add .text.unlikely to TEXT_SECTIONS

gcc's places cold functions into the .text.unlikely section and we
need to check this section as well for section mismatches otherwise we
may have false negatives for this test.

Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: linux-kernel@vger.kernel.org
Cc: linux-kbuild@vger.kernel.org
Signed-off-by: Tom Rini <trini@ti.com>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au> (wording update)