linux-user: Set CF_PARALLEL when mapping shared memory

linux-user: Set CF_PARALLEL when mapping shared memory

Signal the translator to use host atomic instructions for
guest operations, insofar as it is possible.  This is the
best we can do to allow the guest to interact atomically
with other processes.

Resolves: https://gitlab.com/qemu-project/qemu/-/issues/121
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Message-Id: <20210612060828.695332-1-richard.henderson@linaro.org>
Signed-off-by: Laurent Vivier <laurent@vivier.eu>