dma-mapping: fix a Kconfig typo

'thing' -> 'think'
Signed-off-by: Sui Jingfeng <suijingfeng@loongson.cn>
Signed-off-by: Christoph Hellwig <hch@lst.de>

kernel/dma/Kconfig

@@ -39,7 +39,7 @@ config ARCH_HAS_DMA_SET_MASK
 #
 # Select this option if the architecture needs special handling for
 # DMA_ATTR_WRITE_COMBINE.  Normally the "uncached" mapping should be what
-# people thing of when saying write combine, so very few platforms should
+# people think of when saying write combine, so very few platforms should
 # need to enable this.
 #
 config ARCH_HAS_DMA_WRITE_COMBINE