linux-user/ppc: Fix sigmask endianness issue in sigreturn

linux-user/ppc: Fix sigmask endianness issue in sigreturn

do_setcontext() copies the target sigmask without endianness handling
and then uses target_to_host_sigset_internal(), which expects a
byte-swapped one. Use target_to_host_sigset() instead.

Fixes: bcd4933a23f1 ("linux-user: ppc signal handling")
Signed-off-by: Ilya Leoshkevich <iii@linux.ibm.com>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Message-ID: <20241017125811.447961-2-iii@linux.ibm.com>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
(cherry picked from commit 8704132805cf7a3259d1c5a073b3c2b92afa2616)
Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>