dma-mapping: Fix warning reported for missing prototype

lkp reported a warning about missing prototype for a recent patch.

The kernel-doc style comments are out of sync, move them to the right
function.

Cc: Marek Szyprowski <m.szyprowski@samsung.com>
Cc: Christoph Hellwig <hch@lst.de>

Reported-by: kernel test robot <lkp@intel.com>
Closes: https://lore.kernel.org/oe-kbuild-all/202504190615.g9fANxHw-lkp@intel.com/

Signed-off-by: Balbir Singh <balbirs@nvidia.com>
[mszyprow: reformatted subject]
Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
Link: https://lore.kernel.org/r/20250422114034.3535515-1-balbirs@nvidia.com

Author: Balbir Singh

kernel/dma/mapping.c

@@ -910,14 +910,6 @@ int dma_set_coherent_mask(struct device *dev, u64 mask)
 }
 EXPORT_SYMBOL(dma_set_coherent_mask);
 
-/**
- * dma_addressing_limited - return if the device is addressing limited
- * @dev:	device to check
- *
- * Return %true if the devices DMA mask is too small to address all memory in
- * the system, else %false.  Lack of addressing bits is the prime reason for
- * bounce buffering, but might not be the only one.
- */
 static bool __dma_addressing_limited(struct device *dev)
 {
 	const struct dma_map_ops *ops = get_dma_ops(dev);
@@ -931,6 +923,14 @@ static bool __dma_addressing_limited(struct device *dev)
 	return !dma_direct_all_ram_mapped(dev);
 }
 
+/**
+ * dma_addressing_limited - return if the device is addressing limited
+ * @dev:	device to check
+ *
+ * Return %true if the devices DMA mask is too small to address all memory in
+ * the system, else %false.  Lack of addressing bits is the prime reason for
+ * bounce buffering, but might not be the only one.
+ */
 bool dma_addressing_limited(struct device *dev)
 {
 	if (!__dma_addressing_limited(dev))