dmaengine: stm32-dma: rename pm ops before dma pause/resume introduction

dmaengine framework offers device_pause and device_resume ops to pause an
on-going transfer and resume it later.
To avoid any misunderstanding with system sleep pm ops, rename pm ops into
stm32_dma_pm_suspend and stm32_dma_pm_resume.

Signed-off-by: Amelie Delaunay <amelie.delaunay@foss.st.com>
Link: https://lore.kernel.org/r/20220505115611.38845-4-amelie.delaunay@foss.st.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>