mm/kmemleak.c: use address-of operator on section symbols

[ Upstream commit b0d14fc43d39203ae025f20ef4d5d25d9ccf4be1 ]

Clang warns:

  mm/kmemleak.c:1955:28: warning: array comparison always evaluates to a constant [-Wtautological-compare]
        if (__start_ro_after_init < _sdata || __end_ro_after_init > _edata)
                                  ^
  mm/kmemleak.c:1955:60: warning: array comparison always evaluates to a constant [-Wtautological-compare]
        if (__start_ro_after_init < _sdata || __end_ro_after_init > _edata)

These are not true arrays, they are linker defined symbols, which are just
addresses.  Using the address of operator silences the warning and does
not change the resulting assembly with either clang/ld.lld or gcc/ld
(tested with diff + objdump -Dr).

Suggested-by: Nick Desaulniers <ndesaulniers@google.com>
Signed-off-by: Nathan Chancellor <natechancellor@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Link: https://github.com/ClangBuiltLinux/linux/issues/895
Link: http://lkml.kernel.org/r/20200220051551.44000-1-natechancellor@gmail.com


Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>