Ensure stm32_crc_update() and stm32_crc_init() can be called
in atomic context and can't sleep.

Add pm_runtime_irq_safe() to make pm_runtime_get_sync() atomic.
Change runtime pm to call clk_enable()/clk_disable() and change
system pm to unprepare/prepare the clock and force runtime pm
suspend/resume.
Signed-off-by: Nicolas Toromanoff <nicolas.toromanoff@st.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>