drivers: adc: stm32: ADC nocache buffers can be in CONFIG_NOCACHE_MEMORY

CONFIG_NOCACHE_MEMORY is a valid way of declaring buffers in
nocache regions. Consider them valid in the STM32 ADC driver
nocache check.
Copied from commit 818aa2d0

Signed-off-by: Guillaume Gautier <guillaume.gautier-ext@st.com>