rwonce: fix crash by removing READ_ONCE() for unaligned read

rwonce: fix crash by removing READ_ONCE() for unaligned read

When arm64 is built with LTO, it upgrades READ_ONCE() to ldar / ldapr
(load-acquire) to avoid issues that can be caused by the compiler
optimizing away implicit address dependencies.

Unlike plain loads, these load-acquire instructions actually require an
aligned address.

For now, fix it by removing the READ_ONCE() that the buggy commit
introduced.

Fixes: ece69af2ede1 ("rwonce: handle KCSAN like KASAN in read_word_at_a_time()")
Reported-by: Nathan Chancellor <nathan@kernel.org>
Closes: https://lore.kernel.org/r/20250326203926.GA10484@ax162
Signed-off-by: Jann Horn <jannh@google.com>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>