dma-mapping: reduce dma_mapping_error inline bloat

Thanks to the nested inlining, all drivers correctly calling
dma_mapping_error() after a mapping a page or single buffer generate two
calls to get_arch_dma_ops() per callsite, which all adds up to a fair
old chunk of useless code, e.g. ~3KB for an arm64 defconfig plus extras:

text data bss dec hex filename
13051391 1503898 327768 14883057 e318f1 vmlinux.o.old
13050751 1503898 327768 14882417 e31671 vmlinux.o.new

Give the compiler a hand by making it clear we want the same ops.

Signed-off-by: Robin Murphy <[e-mail]>
Reviewed-by: Marek Szyprowski <[e-mail]>
Signed-off-by: Christoph Hellwig <[e-mail]>

include/linux/dma-mapping.h

···
 
 static inline int dma_mapping_error(struct device *dev, dma_addr_t dma_addr)
 {
-	debug_dma_mapping_error(dev, dma_addr);
+	const struct dma_map_ops *ops = get_dma_ops(dev);
 
-	if (get_dma_ops(dev)->mapping_error)
-		return get_dma_ops(dev)->mapping_error(dev, dma_addr);
+	debug_dma_mapping_error(dev, dma_addr);
+	if (ops->mapping_error)
+		return ops->mapping_error(dev, dma_addr);
 	return 0;
 }