FROMLIST: pstore: Make sure CONFIG_PSTORE_PMSG selects CONFIG_RT_MUTEXES

In commit [in -next: 76d62f24] ("pstore: Switch pmsg_lock to an rt_mutex
to avoid priority inversion") I changed a lock to an rt_mutex.

However, its possible that CONFIG_RT_MUTEXES is not enabled,
which then results in a build failure, as the 0day bot detected:
  https://lore.kernel.org/linux-mm/202212211244.TwzWZD3H-lkp@intel.com/



Thus this patch changes CONFIG_PSTORE_PMSG to select
CONFIG_RT_MUTEXES, which ensures the build will not fail.

Cc: Wei Wang <wvw@google.com>
Cc: Midas Chien<midaschieh@google.com>
Cc: Connor O'Brien <connoro@google.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Anton Vorontsov <anton@enomsg.org>
Cc: Colin Cross <ccross@android.com>
Cc: Tony Luck <tony.luck@intel.com>
Cc: kernel test robot <lkp@intel.com>
Cc: kernel-team@android.com
Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: John Stultz <jstultz@google.com>
Link: https://lore.kernel.org/lkml/20221221051855.15761-1-jstultz@google.com/


Change-Id: I56ef91f302aa9ed1be3858c03b72a79543a329e5
[jstultz: Tweaked commit message to avoid catching presubmit checks
 referencing shas that haven't landed upstream yet]
Fixes: 943836e7 ("FROMGIT: pstore: Switch pmsg_lock to an rt_mutex to avoid priority inversion")
Signed-off-by: John Stultz <jstultz@google.com>