mfd: stm32: Enable regmap fast_io for stm32-lptimer

Because stm32-lptimer need to write in registers in interrupt context
enable regmap fast_io to use a spin_lock to protect registers access
rather than a mutex.
Signed-off-by: Benjamin Gaignard <benjamin.gaignard@st.com>
Signed-off-by: Lee Jones <lee.jones@linaro.org>

drivers/mfd/stm32-lptimer.c

@@ -17,6 +17,7 @@ static const struct regmap_config stm32_lptimer_regmap_cfg = {
 	.val_bits = 32,
 	.reg_stride = sizeof(u32),
 	.max_register = STM32_LPTIM_MAX_REGISTER,
+	.fast_io = true,
 };
 
 static int stm32_lptimer_detect_encoder(struct stm32_lptimer *ddata)