docs: dma-api: add a kernel-doc comment for dma_pool_zalloc()

Document the dma_pool_zalloc() wrapper.

Signed-off-by: Petr Tesarik <[e-mail]>
Reviewed-by: Randy Dunlap <[e-mail]>
Tested-by: Randy Dunlap <[e-mail]>
Acked-by: Marek Szyprowski <[e-mail]>
[jc: fixed up dma_pool_alloc() reference in dmapool.h]
Signed-off-by: Jonathan Corbet <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]

Documentation/core-api/mm-api.rst

···
 .. kernel-doc:: mm/dmapool.c
    :export:
 
+.. kernel-doc:: include/linux/dmapool.h
+
 More Memory Management Functions
 ================================
 

include/linux/dmapool.h

···
 				    NUMA_NO_NODE);
 }
 
+/**
+ * dma_pool_zalloc - Get a zero-initialized block of DMA coherent memory.
+ * @pool: dma pool that will produce the block
+ * @mem_flags: GFP_* bitmask
+ * @handle: pointer to dma address of block
+ *
+ * Same as dma_pool_alloc(), but the returned memory is zeroed.
+ */
 static inline void *dma_pool_zalloc(struct dma_pool *pool, gfp_t mem_flags,
 				    dma_addr_t *handle)
 {