[ Upstream commit 31922f62bb527d749b99dbc776e514bcba29b7fe ]

Move STM32 ADC registers definitions to common header.
This is precursor patch to:
- iio: adc: stm32-adc: fix a race when using several adcs with dma and irq

It keeps registers definitions as a whole block, to ease readability and
allow simple access path to EOC bits (readl) in stm32-adc-core driver.

Fixes: 2763ea05 ("iio: adc: stm32: add optional dma support")
Signed-off-by: NFabrice Gasnier <fabrice.gasnier@st.com>
Cc: <Stable@vger.kernel.org>
Signed-off-by: NJonathan Cameron <Jonathan.Cameron@huawei.com>
Signed-off-by: NSasha Levin <sashal@kernel.org>
Signed-off-by: NYang Yingliang <yangyingliang@huawei.com>