spi: fix possible deadlock between internal bus locks and bus_lock_flag

External users may use spi_bus_lock to get exclusive access. This will
also grab the bus_lock_mutex and may therefore result in a deadlock if
__spi_pump_messages also tries to get the mutex.

Therefore adapt spi_pump_messages as well as spi_sync to preset the
bus_locked parameter according to the master->bus_lock_flag.

Fixes: 49023d2e ("spi: core: Fix deadlock when sending messages")
Signed-off-by: Heiko Stuebner <heiko@sntech.de>
Signed-off-by: Mark Brown <broonie@kernel.org>